Secrecy surrounding talks between the UK and Scottish governments to devolve further financial powers to Scotland is akin to the Tartan TTIP, Labour has said.

Shadow Scottish secretary Ian Murray likened efforts to secure a new funding framework for Scotland to the controversial EU-US trade deal - the Transatlantic Trade and Investment Partnership (TTIP) - as he sought assurances it would be agreed before next March.

His remarks came after Scottish Secretary David Mundell accused the Scottish government of being one of the "most centralising governments on record".

Mr Mundell also claimed the SNP were pursuing "grievance and grudge" rather than outlining how it wanted to use any new powers Scotland received.

Speaking during Scotland questions, Labour's Mr Murray asked Mr Mundell: "Scotland's First Minister (Nicola Sturgeon) has warned that the SNP may reject the Scotland Bill if 'the accompanying fiscal framework is not fair to Scotland'.

"It's clear they're looking for any excuse with the fiscal framework to delay further powers for Scotland.

"So can I ask you, can you assure this House that the fiscal framework will be agreed before the Scottish Parliament is dissolved in March and can you explain why both you and the SNP are conspiring to make this agreement the Tartan TTIP, delivered behind closed doors with no public transparency, which begs the question - what are they trying to hide?"

Mr Mundell said a statement had been published after each meeting between UK and Scottish government financial ministers.

He said he took Deputy First Minister John Swinney and the Scottish Government "at face value that they want to reach a fair agreement for Scotland", adding the UK Government wanted this too and he was "confident" this would be achieved.

Earlier in the session, the SNP's Westminster Leader Angus Robertson asked Mr Mundell to explain when the UK Government would provide updates on the progress made on the fiscal framework, which accompanied the Scotland Bill.

The Scottish Secretary said he updated the UK Parliament on Monday.

Mr Robertson then asked for assurances there would be "no detrimental implications" for Scots as a result of the fiscal framework.

Mr Mundell replied: "The reality is the powers that are being delivered to the Scottish Parliament will make it the most powerful devolved parliament in the world.

"But rather than tell us what they'll do with those powers, it's grievance and grudge.

"Will tax credits, which the Scottish Parliament themselves acknowledge can be topped up, be topped up by the SNP? Yes or no?"

Mr Mundell was also asked to deplore the "centralising policies" of the Scottish and Welsh governments by Tory MP Glyn Davies.

The Conservative Cabinet minister replied: "The current Scottish Government is one of the most centralising governments on record, routinely overruling the wishes of local people and local authorities.

"We're delivering devolution to Scotland.

"Let's see, as Lord Smith recommended, devolution delivered within Scotland."

Labour's Ian Austin (Dudley North) questioned why the SNP were asking about more powers for the Scottish Parliament, telling MPs: "The truth is this - they've missed the A&E waiting time in Scotland for six years, more than 6,000 children leave primary school unable to read properly, children from poor families get a particularly bad deal under devolution.

"Scotland is facing a housing crisis and when I visited Edinburgh a week or so ago I was stunned at the level of rough sleeping in that city, much more than in comparable cities.

"So shouldn't they be sorting out the things for which they're responsible instead of demanding all these more powers.

"They're not just the most centralising, but the most useless."

Mr Mundell reiterated the Scotland Bill would make the Scottish Parliament the most powerful devolved government in the world, adding the SNP and MSPs needed to outline how they would use the new powers.

He said: "They prefer arguments about process, they don't want to tell us what they're going to do and they don't follow that through with action."

Tory MP Bob Blackman said the Scottish Government should use its tax-raising powers to pay for services to Scots rather than "relying on subsidies from London".

Mr Mundell said he did not recognise Mr Blackman's description of the Barnett Formula, with the SNP continually pressing the Scottish Secretary to disassociate himself from Mr Blackman's remarks.

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