David Cameron has warned his successor as prime minister cannot guarantee Wales' EU funding will continue following the Brexit vote.
Speaking at Prime Minister's Questions, he said they did "not know exactly what will happen to our economy in the event of a leave vote" so it was "difficult for anyone to give guarantees".
"As I said throughout the campaign, if the vote was a No vote, I would want to do everything I could to make sure that we continued to help disadvantaged regions and our farmers.
"But it will be a matter for my successor as we leave the EU to make good on what they said at the time".
He was responding to a question from Torfaen MP Nick Thomas-Symonds who asked if the Prime Minister agreed that if his constituency "loses a penny piece of its funding under his successor, that would be a gross betrayal".
52.5 per cent of Welsh voters backed leaving the EU during the referendum last week despite the region enjoying an annual net benefit of £245m from the UK's membership, according to a study by Cardiff University.
Senior figures in the official Vote Leave campaign, including Boris Johnson, Michael Gove and Chris Grayling, said there would be "more than enough money" to finance the projects currently run by the EU.
In an open letter earlier this month, they stated that all programmes were funded at their current levels up until 2020, and that they could then run them "much more effectively" and free up extra money to spend on "other priorities".
The leader of the Welsh Conservatives, Andrew RT Davies, told the BBC at the time: "Despite the First Minister's fantasy claims, we now know that funding for each and every part of the UK, including Wales, would be safe if we vote to leave.
"The real danger therefore lies in voting to remain, where EU leaders have imposed stringent cuts to regions across the European Union."
Wales' First Minister Carwyn Jones has called for the Welsh government to be involved in negotiations over the terms of Brexit.
Speaking to his cabinet in Cardiff Bay on Monday, he said the final deal must be approved by all four UK parliaments, but the Welsh government ultimately had to respect the vote to leave.
He said his government would use "every lever at our disposal" to protect Welsh communities.
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