The European Research Group: who are they?

– What is the European Research Group (ERG)?

Officially, the ERG is described, as the name suggests, as a research service providing briefings for Conservative MPs on issues relating to the UK’s membership of the European Union.

Critics, however, accuse it of acting as a “party within a party”, running its own whipping operation in support of its objective of a so-called “hard” Brexit, if necessary leaving without any deal with Brussels.

– So how did it come about?

It was originally formed in the early 1990s by Eurosceptic rebels opposed to John Major signing the Maastricht Treaty led by the then Conservative MP Sir Michael Spicer.

Following the 2016 EU referendum, it relaunched under the leadership of Tory backbencher Steve Baker with the declared aim of opposing a “fake” Brexit.

When Mr Baker became a Brexit minister in 2017 he was replaced as chairman by Suella Braverman and, when she joined the Government the following year, Jacob Rees-Mogg took over.

Mr Baker and Ms Braverman subsequently returned after quitting over Theresa May’s Chequers plan and Mr Baker is currently the deputy chairman.

– How many members does it have?

It is hard to know exactly as it does not publish an official membership list.

However an indication of the strength of its support came in February 2018 when 62 MPs signed a letter from the group calling on Mrs May to stick by the principles set out in her Lancaster House speech the previous year.

Signatories included former leader Iain Duncan Smith, ex-cabinet ministers Owen Paterson and Priti Patel, and the veteran Eurosceptics John Redwood, Sir Bill Cash and Sir Bernard Jenkin.

Since his resignation, former Brexit secretary David Davis has appeared at events alongside ERG supporters and a number of current ministers, both inside and outside the Cabinet, are thought to be sympathetic to its aims.

– How effective are they?

The record here is rather mixed.

In November the group was widely ridiculed when Mr Rees-Mogg publicly called on Tory MPs to lodge letters of no confidence in Mrs May, only to fall flat on his face when the 48 submissions required to force a contest failed to materialise. There was a vote the following month which Mrs May survived.

However Thursday’s Commons vote, when the group announced a “collective decision” to abstain just minutes before MPs began trooping through the division lobbies underlined that it remains a force to be reckoned with.

The result was another heavy defeat for the Prime Minister, with more than a fifth of the party in the Commons refusing to support her.

Mrs May’s slender Commons majority effectively gives the group a veto over any Brexit plan she brings forward unless she can win support from MPs from other parties.