IAIN Duncan Smith is facing a rigorous campaign by pro-EU activists to dethrone his 25-year reign as MP for Chingford.

The 63-year-old is on an “attack list” of 20 Leave-supporting MPs as Remain campaigners look to target the north-east London seat for tactical voting.

Successor groups to the Remain campaign, Open Britain, European Movement and Britain for Europe want to reduce the number of hard Brexit-supporting MPs during the two-year negotiations.

Among Mr Duncan Smith on the list are Labour’s MP for Vauxhall Kate Hoey, Tory ex-minister Theresa Villiers and MP for Enfield Southgate, David Burrowes.

The former work pensions minister had an 8,386 majority in Chingford and Woodford Green in 2015, but his seat voted to remain in the EU by 51%.

He told the Guardian campaigners were "welcome" to target his seat, but claimed there was no point fighting the referendum again.

Labour's former cabinet minister Lord Mandelson, an Open Britain board member, said: "As a former European trade commissioner, I have seen such negotiations from the inside.

"For Britain to get the best possible trade deal, it is totally counter-productive for Theresa May to go into them with a rigid set of red lines."