New sites should be used for nuclear plants, Mr Brown said
Gordon Brown has said the UK needs to increase its nuclear power capacity - raising the prospect of plants being built in new locations.
The prime minister said that with oil prices soaring, it was time to be "more ambitious" for nuclear plans.
No 10 sources said it was "open" as to whether new sites might be needed.
Ministers announced in January they backed new plants, but the focus was on replacing existing nuclear capacity as plants reached the end of their life.
And a review of possible sites published at the same time focused on 14 locations where there have been nuclear power plants before.
Since then Business Secretary John Hutton has said he wants the nuclear industry to go beyond replacing its 23 ageing reactors, which provide 20% of the UK's electricity.
He has said no "artificial cap" will be put on the proportion of electricity to be generated by this or any other source of "low-carbon energy".
EXISTING GOVERNMENT PLANS
Speed up planning process to make it easier to build plants
No public subsidies for nuclear except in emergencies
No limit to amount of electricity generated by nuclear power
New independent body to monitor decommissioning costs
Trebling of investment in wind and wave power
Store nuclear waste at 'interim' facility until suitable underground site found
But Mr Brown's comments are the first time he has said explicitly that building plans for nuclear plants should be expanded beyond merely replacements.
Speaking to oil industry representatives in Banchory, near Aberdeen, Mr Brown said: "We want to do more to diversify our supply of energy and that's why I think we are pretty clear that we will have to do more than simply replace existing nuclear capability in Britain.
"We will be more ambitious for our plans for nuclear in the future."
Downing Street sources said plans could involve expanding existing nuclear power stations or building plants on new sites.
Energy companies, rather than the government, build power stations and the January statement was important in encouraging private firms to invest in new plants.
The planning system is already being changed to make it easier for key infrastructure projects such as nuclear power to get planning permission.
French firm EDF has said it plans to construct four plants without subsidies in the UK - the first by 2017.
But critics of nuclear energy say it is expensive, creates radioactive waste and could become a target for terrorists.
Greenpeace claims that even 10 new reactors would cut the UK's carbon emissions by only about 4% some time after 2025.
Liberal Democrat environment spokesman Steve Webb said: "Gordon Brown is drawing totally the wrong conclusion from soaring oil prices. New nuclear power plants won't deliver any power for over a decade.
"Nuclear power is not the answer to today's energy crisis. The government should be focusing on greater energy efficiency, boosting renewables, and making sure that coal-fired power stations do not pollute the environment."
In January the Conservatives backed the building of new nuclear power plants as long as no public subsidy was involved.
Energy policy is not a devolved matter but Scottish First Minister Alex Salmond has said there is "no chance" of more nuclear power stations being built in Scotland.
No new plants have been built in the UK since Sizewell B, which opened in 1994.