The SNP's Westminster leader has pledged to ensure an early debate and vote on Trident, calling on Jeremy Corbyn not to abandon his long-standing opposition to its renewal.

Angus Robertson MP urged Mr Corbyn not to perform a U-turn on the UK's nuclear deterrent, despite a large swathe of his MPs not seeing eye-to-eye with their leader on the issue.

A crunch vote on the renewal of Trident is expected within months after the Government completes a Strategic Defence and Security Review, examining the threats facing the country in the years ahead.

The SNP has called on Scottish Labour leader Kezia Dugdale to clarify her position ahead of an expected debate on the issue at the Scottish Labour Party conference later this month.

Mr Robertson told the SNP's conference in Aberdeen that the party would continue to "resolutely" oppose Trident and would be "happy to help" Mr Corbyn by calling an early debate and vote on Trident in the House of Commons.

He said Labour's U-turn over last night's vote on the Conservative Charter of Budget Responsibility, during which 21 MPs rebelled against Mr Corbyn and voted for it, was a "welcome change of heart".

Mr Robertson said: "Can I just say to Jeremy Corbyn that one U-turn that he can't consider is ditching his principled career-long opposition to Trident.

"Labour weren't prepared to have a specific debate on Trident at their conference. I am pleased that the SNP is debating it here at our conference.

"I'm also happy to help Jeremy Corbyn and ensure that there is an early debate and vote at Westminster aimed at opposing Trident renewal.

"Hopefully Jeremy will join the SNP in the lobbies as he has often done in the past in opposing Trident, although I am not holding my breath that he can bring his colleagues in the Parliamentary Labour Party with him."

Mr Robertson said SNP MPs were now the "effective opposition" to the Tories at Westminster and had ensured "embarrassing" U-turns from the UK Government, including on fox-hunting.

He said: "That was the fourth issue where the SNP Group led the opposition in forcing the Tories into backing down in less than two months.

"Our effective opposition stopped the EU referendum being on the same day as the Scottish Parliament election.

"We ensured any moves to repeal the Human Rights Act were kicked into the long grass, and there was the debacle over abandoning a vote on English Votes for English Laws.

"This is another powerful reminder of just how fragile the Tories' majority is. On these four issues it was non-existent. They were staring defeat in the face and there will be many more such issues which we will pursue as the effective opposition."