David Cameron has vowed to examine licences for the sale of arms to Russia after claims they breached a ban.
It comes after MPs warned that export licences for the sale of arms, including components for anti-aircraft guns, remained in place despite fears Moscow was arming rebels in Ukraine.
No 10 said the UK had not sold arms to Russia's armed forces since March.
The prime minister said he was confident that remained the case but the claims would be examined in detail.
He said: "I believe that we have been consistent with the terms of the arms embargo that we set out which was principally aimed at Russian armed forces and the use of goods and involvement in Ukraine but we will look very carefully at all outstanding licences and make sure that's the case and of course if it's not the case we would want to act very swiftly."
Mr Cameron has criticised other EU countries' arms deals with Moscow, and his spokesman has said the arms export licences still in place are for "non-military legitimate reasons".
Mr Cameron added that the government "will need to go through each one of these(licences) individually" to make sure they met the terms of the embargo.
In March, then Foreign Secretary William Hague told MPs: "The UK will now, with immediate effect, suspend all extant licences and application processing for licences for direct export to Russia for military and dual-use items destined for units of the Russian armed forces or other state agencies which could be or are being deployed against Ukraine."
The cross-party Commons Committees on Arms Export Controls said 31 UK licences had been halted or suspended.
But permits covering sniper rifles, night sights, and components for air-to-air missiles, anti-aircraft guns, combat helicopters, depth charges and rocket launchers, remained in force, it said.
Arms export licences
UK arms exports to Russia
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Exports of small arms ammunition, gun mountings, body armour, military communications equipment and "equipment employing cryptography" are also still permitted, the committee added.
A total of 251 licences worth at least £132m remained in force, it said.
The government said it was keeping all licences under review and the majority of licences that remained in place were for "commercial use".
A spokesman for the Department for Business, Innovation and Skills said some of the items, including the anti-aircraft guns, were destined for the Brazilian Navy, which would access the equipment at Russian ports.
"This government has never exported missiles or missile parts to the Russian military," he said.
Export licences for rifles and ammunition covered hunting and sporting rifles supplied to private individuals and to authorised dealers for resale, the spokesman added.
Defence Secretary Michael Fallon said Britain did not export arms to the Russian armed forces "that could be used for internal repression".
"That's always been an absolutely standing policy. We have one of the strictest arms sale policies in the world. There is no equipment at all now that's being sold to Russia that could possibly be used to Ukraine," he told BBC News.
Mr Cameron has criticised European countries such as France which are continuing to pursue defence sales to Russia despite Moscow's backing for the separatists.
But France's Foreign Minister Laurent Fabius hit back on Monday, suggesting Britain should look at the number of Russian oligarchs in London before criticising his country.
Downing Street rejected charges of "hypocrisy" over the prime minister's approach to Russia, saying there had been no criticism of Mr Cameron from "around the EU table".
"The PM and other EU leaders are entirely focussed on what should be done following the terrible loss of life rather than raising other issues," said a source.
Mr Cameron is under fire over a £160,000 donation to the Conservative Party from the wife of a former member of President Putin's government, who bid for a game of tennis with the prime minister and London mayor Boris Johnson at a fundraising ball in London.
A Tory spokesman said the party was not considering repaying the donation, from Lubov Chernukhin, because it was within the rules and would be declared to the Electoral Commission.
The spokesman said Mrs Chernukhin's husband Vladimir, who was a Russian finance minister, was sacked in 2004, had fallen out with President Putin and did not have links with the Putin regime. He said the couple were now both British citizens.
The spokesman said he was confident all the donations from donors with Russian links were in order and complied with the rules.
Moscow's support for pro-Russian groups in Ukraine has come under renewed scrutiny after the fatal crash of Malaysian airliner MH17 with 298 people on board, which the UK and US believe was shot down by a surface-to-air missile launched from a rebel-held area.
The prime minister has said EU nations should consider stopping all military sales to Russia, while Foreign Secretary Philip Hammond said an embargo on future arms contracts was under consideration following a meeting in Brussels on Tuesday.
Sir John Stanley, the Conservative MP who heads the committee, said the relatively small number of licences which had been withdrawn reflected the "circumscribed" nature of the UK's moratorium, which he said referred only to equipment which could be deployed against Ukraine and did not cover Russia's wider defence needs.
While he said that Britain had been in the vanguard of European countries in taking action to curb defence sales to Russia, it had still not gone far enough.
"Russia is an authoritarian regime. We should have been applying a more cautious approach for some time in regard to Russia," he said.
Sir John has written to Mr Cameron asking if he will be suspending or revoking the remaining licences. He has also written to Business Secretary Vince Cable asking for details of the "end-user for each licence".
The committee also strongly criticised the award of licences for the export of chemicals which could be used in the manufacture of chemical weapons to Syria.
It said the award by the previous Labour government of five licences for the export of sodium fluoride had been "highly questionable", while the decision of the current government to issue a further two licences for sodium and potassium fluoride after the civil war had begun was irresponsible.
It said that the current government's claim that it had no grounds to refuse the licences was "grossly inaccurate".
The committee - which is made up of the Commons foreign affairs, defence, international development and business, innovation and skills committees - also expressed concern ministers had watered down their policy on the export of equipment to countries where there were concerns it could be used for internal repression.
It said that a "broad" test that an export licence should not be issued if there was "concern" the equipment could be used for internal repression had been dropped from the latest set of government guidelines issued earlier this year, and only the "narrow" test that there had to be a "clear risk" of repression remained.
A government spokesman said the UK aimed to operate one the most robust and transparent export control systems in the world, and that "every application is examined rigorously against internationally-recognised criteria and particular attention is paid to human rights risks".