Russian President Vladimir Putin is "waiting in the wings" to bring Greece under his sphere of influence if the country's third bailout plan goes awry, Harriet Harman has warned.

The interim Labour leader issued the stark warning to Greece's lenders and David Cameron as she debated the Conservative leader at Prime Minister's Questions (PMQs) on 15 July.

"With president Putin waiting in the wings, this is about more than just economics – it's got wide geopolitical significance," Harman said.

Cameron said he agreed with the acting leader of the opposition "about the dangers of Russian involvement", but the prime minister stressed that bailing out Greece was a matter for eurozone countries.

He said: "Greece is a member of the EU, as well as a member of the euro, it is a friend and ally of Britain – we are Nato members, we are trading partners – but it's not for Britain to bailout eurozone countries, and we wouldn't do that.

"But as a member of the EU, if Greece were for instance to leave the euro and wanted humanitarian assistance, I'm sure that this house and the British public would take a more generous view."

IMF issues warning

The exchange in the House of Commons comes after the International Monetary Fund (IMF), one of Greece's lenders, criticised the country's bailout conditions.

The US-based organisation warned that the struggling state's public debt had become "highly unsustainable".

"Greece's debt can now only be made sustainable through debt relief measures that go far beyond what Europe has been willing to consider so far," the IMF said in a report released on 14 July.

The publication of the statement comes just hours before the Greek parliament is set to vote on the conditions of the country's new bailout terms, which include a condition for the Syriza government to sell off €50bn (£36bn, $55bn) worth of assets.

Greek Prime Minister Alexis Tsipras is expected to get the backing of MPs but he will likely have to reshuffle his cabinet after the vote, according to Open Europe policy analyst Vincenzo Scarpetta.

He told IBTimes UK on 13 July: "The most likely outcome that I can see is that the measures are passed thanks to a broad national unity coalition in the parliament.

"We have already seen the factions within Syriza and I think the hard-line left fringe will not vote for this deal.

"That will mean that the prime minister does not really have a majority in parliament anymore and any scenario would be open, including a cabinet reshuffle, a national unity government or Tsipras resigning and, potentially, new elections."

Tsipras, who came to power on a left-wing surge at the start of 2015, has met with Putin throughout his country's debt crisis.

The Greek premier attended the International Economic Forum in June, where he reportedly said Russia had a "big role to play" with Greece, according to Canada's Globe and Mail.