Sir Keir Starmer, shadow Brexit secretary, accuses David Davis of using legislation to hand “unprecedented and undemocratic powers” to ministers and grabbing power from Northern Ireland and Scotland

Labour is to launch an all-out assault on the government’s “undemocratic” and “unacceptable” plans to legislate for Brexit, setting the scene for months of parliamentary warfare.

Ministers are due to introduce the so-called Great Repeal Bill for its second reading in the House of Commons on Thursday.

The bill incorporates most existing EU law into domestic legislation while repealing the act that took Britain into the EU in 1973.

But in a sign of the parliamentary battles ahead, Labour has written to David Davis, the Brexit secretary, demanding wholesale changes to the legislation and warning that it fails to guarantee “crucial rights and protections” for citizens.

Significantly the letter, which has been passed to The Times, calls for the bill to be altered to