Gordon Brown has used his first speech in the Commons since stepping down as prime minister to call for work on the UK's two new aircraft carriers to be carried out near his constituency.
He said maintenance contracts should be carried out at Rosyth - bordering his Kirkcaldy and Cowdenbeath seat - amid concerns the work could go to France.
HMS Queen Elizabeth and HMS Prince of Wales were spared from defence cuts.
The government said it was "extremely likely" the UK would retain the work.
Mr Brown's speech came as Labour MP Thomas Docherty put forward a motion examining options for the ships.
On Tuesday the UK and France are due to sign two defence treaties. The co-operation is likely to lead to the shared use of aircraft carriers and could see British and French planes flying from ships belonging to either nation.
The former prime minister told MPs that Rosyth was the "only base that can assemble the aircraft carriers that have been commissioned by this country".
He said: "These are military decisions made on military advice for military reasons. And the reason that these decisions have been made is this: that if we are to retain a global presence as a navy, as armed forces and as a country, then we will need these aircraft carriers in the years to come."
He said the workforce at Rosyth were "skilled, educated and trained people who have given their lives to the service of this country".
The £5.4bn aircraft carriers deal has proved controversial.
The government ruled out cancelling one of the carriers, which are due to enter service in 2016 and 2019, as part of cuts to spending because it said it would cost more than going ahead with both.
Ahead of Mr Brown's speech, Conservative MP Bernard Jenkin had said the former PM should apologise for the aircraft carriers deal, saying: "His appearance in this debate shows that his decision to order the aircraft carriers was always about protecting his own interests rather than the national interest."
But the former head of the armed forces, Sir Jock Stirrup, told the BBC on Sunday that the aircraft carriers deal had been done for "entirely sensible" reasons - to persuade the UK's shipbuilding industry to scale down and invest in rationalisation.
Responding to Monday's debate, defence procurement minister Peter Luff said no decisions had been made on long-term maintenance contracts but the "main investment decision for support arrangements" would be taken "before the middle of this decade".
"A number of options are being considered for the future support of the Queen Elizabeth class, including facilities at Rosyth together with other UK and possibly overseas locations - all with sufficiently large facilities. There are more than two yards that can actually do this work," he said.
When Mr Brown pressed him for an assurance that the refit would take place in the UK, Mr Luff said: "I think it is extremely likely that they will, but I cannot rule out the possibility that they will not. The assumption is they will be refitted in the UK."
Mr Brown, who has been working on a book about the financial crisis, has not addressed the Commons since before Labour's general election defeat in May.
While his Commons speech was met with cheers from Labour backbenchers, there were jeers from some coalition MPs.
Tony Blair, Gordon Brown's predecessor as prime minister, stood down immediately as an MP after leaving No 10 in 2007.
However, former Conservative prime minister Ted Heath remained as an MP for more than 25 years after losing the leadership of his party and made frequent speeches in the Commons from the backbenches criticising Tory policies.
Former Conservative Cabinet minister Michael Portillo said prime ministers, particularly Lady Thatcher, struggled to adapt to life as a backbencher after losing power.
"I think the loss of office is an extreme bereavement," he told BBC Radio 4's Today.
There was always a risk that former leaders could become a "rallying point for dissidents" if they remained in the Commons, he added, but that this was unlikely to be the case with Mr Brown as it was "pretty clear his generation has moved on".