The BNP would offer non-white British people £50,000 to leave "overcrowded" Britain and return to the land of their ancestors, the party's leader Nick Griffin said today.

Griffin said the voluntary programme would be open to around 180,000 people a year who "could go back and help develop their own countries". He said the scheme would be funded from the foreign aid budget and money the government is "wasting at the moment on ridiculous climate change adaptation policies".

"We're saying that we'd give resettlement grants ... this is voluntary ... we're looking probably at £50,000 per person," he told BBC Radio 4's Today programme.

Griffin said that the doors would be closed to everyone because Britain was "the most overcrowded country in Europe", but he did give exceptions. He said that Irish people would be allowed in because "as far as we are concerned the Irish are part of Britain and are fully entitled to come here".

Griffin also gave the example of a Japanese physicist needed to help with a fleet of British-built nuclear power stations to be developed under a BNP government. He claimed that French people who came to the country were unlikely to be targeting "soft-touch Britain".

"If you are talking about Polish plumbers or Afghan refugees, the doors are going to be shut because Britain is full," the BNP leader said.

Griffin, who claimed he would rather be about the economy "like the other leaders", but was "very pleased" to talk about immigration, continued: "The door is shut to any significant numbers whatsoever, from anywhere. It's open where it suits Britain and suits the British people. That's fair enough."

He claimed "British indigenous" people would be in a minority in the country between 2050 and the end of the century.

Griffin said the BNP would be prepared to tear up international treaties in order to achieve its objectives. Asked what would happen if other countries reciprocated by not allowing British people in, Griffin replied: "The last thing I saw there wasn't a queue of Brits trying to go to Albania or Somalia."