THE risks of a "miscalculation or a misstep" leading to a very bad outcome in the Greek debt crisis are growing, George Osborne has warned.

The Chancellor's fears came as Panos Kammenos, the Greek Defence Minister, suggested that if his country failed to get a new debt agreement with the eurozone, it could adopt "Plan B ... to get funding from another source" "It could the United States at best, it could be Russia, it could be China or other countries," Mr Kammenos said.

Speaking at a meeting of G20 finance ministers in Istanbul which has been dominated by Greece's debt woes, Mr Osborne acknowledged that a crisis in the eurozone would spill over to affect the UK and warned of the dangers of a "chaotic and disorderly exit".

"There's no doubt that the UK economy would be affected by a crisis in the eurozone," he explained.

"It's why it is vital that we go on working through our economic plan so that we are taking steps to secure and strengthen our economy."

The Chancellor's remarks come after Prime Minister David Cameron met officials from the Treasury and Bank of England in Downing Street earlier this week to discuss measures to protect Britain from the "contagion" caused by a Greek debt default or exit from the euro.

Alexis Tsipras, Greece's new left-wing premier, who was elected last month on an anti-austerity platform, has insisted he is confident of reaching a deal on the £240 billion national debt, which his Syriza party blames for six years of deep recession.

It remains unclear whether compromise can be reached today at an emergency meeting of eurozone finance ministers in Brussels. German Chancellor Angela Merkel has said she is waiting to see whether Athens puts "a sustainable proposal" on the table.

In Istanbul, Mr Osborne warned: "It's clear to the world economy that this stand-off with the eurozone and Greece is growing each day and the risks of a miscalculation or a misstep leading to a very bad outcome are growing as well.

"Here at the G20, we are urging all parties to this dispute to try and find some common solutions and we are also at home stepping up our preparations for whatever the outcome may be."