THERESA May changed a keynote Brexit speech after facing the charge of "utter hypocrisy" over her call to MPs not to subvert democracy by refusing to honour the 2016 referendum vote to leave the EU.

Parliamentary records show that in 1998 the Prime Minister was among 144 MPs who voted for an amendment that would have blocked the Government of Wales Bill giving effect to the 1997 referendum result to create the Welsh Assembly.

A Downing Street trail of Mrs May’s speech said she would highlight how the result of the 1997 Welsh vote had been "accepted by both sides,” despite being carried by a majority of just 0.6 per cent.

She was also due to say the "popular legitimacy" of the Cardiff legislature had “never been seriously questioned" in a section of the speech drawing a parallel with the EU poll result.

But, when the PM delivered it in Brexit-supporting Stoke-on-Trent yesterday, the key section had been altered with Mrs May, rather than referring to “both sides,” instead said the Welsh devolution result had been “accepted by Parliament".

Reference to the legitimacy of the assembly had also been excised with, instead, the PM saying: "Indeed, we have never had a referendum in the UK we have not honoured the result of."

In an appeal to colleagues, she declared: "The House of Commons did not say to the people of Scotland or Wales that despite voting in favour of a devolved legislature, Parliament knew better and would overrule them. Or else force them to vote again.”

In their 2005 manifesto, the Conservatives suggested the people of Wales should vote again following the 1997 devolution poll “on whether to keep the Welsh Assembly in its current form, increase its powers or abolish it".

Commenting on the trail of the PM’s speech, Labour’s Jo Stevens, who represents Cardiff Central, claimed it exposed "yet more utter hypocrisy from the PM, who, with other leading Brexit Tories, voted against legislation giving effect to the result of the Welsh referendum before it was implemented".

In Scotland, the SNP’s Joan MacAlpine also went on the attack, pointing out how Mrs May had backed a wrecking amendment to the 1998 Scotland Bill and accused her of “brazen hypocrisy”.

Asked how the PM countered such a charge, her spokesman said: “What we are talking about today – I don’t propose to examine in detail the reactions of the Conservative Party 20 years hence – is there are some people calling for a second vote on an event that has not yet happened ie us leaving the EU; what the PM was saying was she does not believe that to be the right thing to do.”

Asked if the PM regretted using the example of the Welsh referendum, he replied: “What the PM set out in her speech was right and reflected precisely the situation she describes. Obviously, there was some information in the trail which…was not quite right and we hold our hands up to that.”