Nicola Sturgeon has warned Downing Street there should be "no blocking mechanisms" applied to her plans for a second independence referendum.

The First Minister also insisted the timing of the referendum should be determined by Scotland and not by London.

Prime Minister Theresa May was meanwhile barracked by MPs as she told the House of Commons she had been "working closely" with the Scottish Government on preparations for Brexit.

Speaking after a meeting of her senior ministerial team on Tuesday, Sturgeon said: "Cabinet today agreed that the referendum must be for Scotland's national legislature to shape.

"It should be up to the Scottish Parliament to determine the referendum's timing, franchise and the question."

Sturgeon insisted the Scottish Government "has a cast-iron democratic mandate for an independence referendum".

The SNP leader said: "The vote must take place within a timeframe to allow an informed choice to be made - when the terms of Brexit are clear but before the UK leaves the European Union or shortly afterwards.

"In that way, with the vote taking placed between the autumn of 2018 and the spring of 2019, the independence prospectus which we will offer people can be contrasted directly with the Brexit deal which the UK Government will have negotiated by the start of that period."

In a swipe at Sturgeon's plans for an independence referendum, May told the Commons: "This is not a moment to play politics or create uncertainty.

"It is a moment to bring our country together, to honour the will of the British people and to shape for them a better, brighter future and a better Britain."

May also confirmed she expected royal assent to be granted "in the coming days" to the bill granting her the power to begin Brexit negotiations with the EU.

She also promised to come to the Commons before the end of March to inform MPs that she had triggered withdrawal talks under Article 50 of the EU treaties.

May's comments were seen as an indication she will not allow a second independence referendum to go ahead until after the Brexit process is complete - which is expected to be in the spring of 2019.

Some reports have suggested permission could be conditional on the SNP gaining an absolute majority in the 2021 Scottish election.

Sturgeon responded to the Prime Minister by highlighting the 2015 general election results and pointing out May took the keys to Number 10 without an election, or even completing a Tory leadership contest.

On Twitter, she said: "A quick reminder: Tory vote in GE2015 - 36.9% SNP constituency vote in SP2016 - 46.5%.

"Trading mandates does not put PM on strong ground.

"In addition, I was elected as FM on a clear manifesto commitment re #scotref. The PM is not yet elected by anyone."

After the Scottish cabinet met at Bute House, Sturgeon said: "Scotland's referendum should be built on the principles of democracy, mandate and precedent, all of which should be observed as we move to give the people of Scotland the choice the current political situation demands.

"There should be no strings attached, no blocking mechanisms applied and no Downing Street diktat - Scotland's referendum must be made in Scotland."

She added: "That was the exact description the UK Government themselves used ahead of the 2014 referendum and the same principle should apply now."