Four government departments spent almost £6m ensuring their websites appeared on search engine results pages in the last two financial years, according to newly released figures.
The Department of Health was the biggest spender, running up a bill of £4.4m in "paid search" fees.
It said the money was spent supporting campaigns on smoking and the flu pandemic.
Organisations can pay search engines to ensure their websites appear at the top of users' searches. They are often charged for each person who accesses their sites via the link.
The Department for Communities and Local Government spent over £750,000 promoting campaign websites including those for Home Information Packs, Eco Towns and Energy Performance Certificates.
The Department of Energy and Climate Change spent more than £309,000 last year. The Department of the environment, food and rural affairs (Defra) spent almost £500,000.
An energy department spokesman said: "This has been used primarily as part of the "Act on CO2" campaign, which helps people to find ways to reduce their carbon emissions and save money through reducing their energy use."
Defra said it had also spent money on promoting Act on CO2 and other environmental campaigns, including Muck In4Life, which informs people about environment-related activities in their area.
A Defra spoeksman said: "As search engines have become an increasingly important method for accessing information - over 1.2 billion searches are conducted every month in the UK and 88% of internet users regularly visit search engines - this spending is a cost-effective way of getting important information to a large audience."
The Department of Health said no new commitments had been made since a moratorium on government marketing was put in place.
The government announced a review of existing marketing projects and a freeze on new expenditure alongside its first major announcement about spending cuts in May.
Conservative MP Damian Hinds, who uncovered the figures in a series of Parliamentary questions, said: "Of course there are times and subjects when getting the information out there is an absolute imperative.
"But in general I don't see why government departments should spend large sums improving their showing on search engines.
"I would have thought the search engines themselves should ensure official information is easy to find."