Alberto Costa was forced as Parliamentary Private Secretary (PPS) to David Mundell after lodging an amendment calling for the UK to seek agreement with Brussels on citizens rights even in a no-deal - even though his proposal was accepted by ministers.

Addressing MPs after losing his job in government, Mr Costa said it was a “very sad state of affairs” that his amendment was needed, and said the rights of EU citizens in the UK and Britons living in the EU “should never have been used as a bargaining chip”.

The amendment passed without a vote last night, with the government avoiding likely defeat after more than 140 MPs from all parties said they backed it.

MP Alberto Costa. Picture:: Chris McAndrew/UK Parliament

Born in Scotland to Italian parents who have lived in the UK for decades without claiming British citizenship, Mr Costa has sought firm guarantees for EU citizens in all Brexit outcomes since the referendum in 2016. He was knighted by the Italian government in 2017 for his campaigning on behalf of European citizens.

The Prime Minister’s spokespeople said Mr Costa had resigned after breaking the convention that members of the government do not put down amendments to government business.

However, one government source said the South Leicestershire MP had been called in to the whips’ office shortly before quitting. Another source confirmed that Mr Costa had been “sacked”.

It sparked anger in the Scotland Office and many Tory MPs, with whom Mr Costa is a popular figure. One source at Dover House said Mr Costa was a “huge asset” to Mr Mundell’s department and described his exit as a “loss”, while another was quoted as saying his treatment had been “appalling”.

In a post on social media, the Scottish Secretary said he was “very sorry” to lose Mr Costa has his PPS. At Holyrood, the Tory finance spokesman Murdo Fraser called the sacking “hard to understand” and said Mr Costa “should be rewarded not punished”.

Mr Costa met with Theresa May following his resignation, and her spokespeople stressed the Prime Minister’s “deep admiration” for his work.

There had been confusion earlier in the day when Home Secretary Sajid Javid told the Commons Home Affairs Committee that he saw “nothing” wrong with the amendment, only for SNP MP Stuart McDonald to point out the Prime Minister had suggested it was legally unworkable the day before.

Mr Costa told the Commons that citizens’ rights “should never have been used as a bargaining chip during the negotiations for our withdrawal from the EU. That such rights were placed on the table in the first place was wrong.” Rights should have been ‘ring fenced’ in negotiations “at the outset”, Mr Costa added.

Mr McDonald said it was “shameful, and deeply ironic, that the first time someone in the Scotland Office actually does their job... they are swiftly given the sack”.

Brexit: Sacked Scottish MP says EU citizens used as ‘bargaining chip’