Deputy Labour leader Tom Watson has urged an “amnesty” for party members who voted Liberal Democrat or Green in the European elections.

He attacked “spiteful” moves to expel people like former Blair spin doctor Alastair Campbell after they admitted backing rival parties in the poll last week.

Campbell was sent an email by Labour’s HQ informing him he had automatically expelled himself by declaring on BBC TV on election results night that he had voted for Vince Cable’s party.

But Watson, who is pushing for members to formally be allowed to toughen up Labour’s policy on a second Brexit referendum, said that thousands of supporters had sent Jeremy Corbyn a similar message in the elections.

Some Labour members in Scotland voted SNP, in Wales they voted Plaid, but across England many backed the Lib Dems or Greens.

“It is very clear that many thousands of Labour Party members voted for other parties last week. They were disappointed with the position on Brexit that a small number of people on the NEC inserted into our manifesto,” Watson said in a statement.

“They were sending the NEC a message that our position lacked clarity and they were right. It is spiteful to resort to expulsions when the NEC should be listening to members.”

He added that the “politics of intolerance” holds no future for the Labour Party. “A broad church party requires pluralism and tolerance to survive. There should be an amnesty for members who voted a different way last week. We should be listening to members rather than punishing them.”

Labour emailed Campbell on Tuesday to tell him that his actions were “incompatible with party membership”. 

The former No.10 strategy and comms chief, who has been a long-standing advocate for a so-called people’s vote on EU membership, tweeted that he was “sad and disappointed” by the news – and that he may launch a legal challenge. 

A growing #expelmetoo campaign emerged on Tuesday night after Campbell’s expulsion.

Former party rulebook chief Mike Creighton leapt to Campbell’s defence, stating that declaring a vote for a party after a poll had closed was not considered a breach of membership.

His view was echoed by former deputy leader Harriet Harman.

Former Labour home secretary Charles Clarke called on Labour to reinstate Alastair Campbell, as he admitted he also voted Liberal Democrat in the European elections

Clarke, a senior figure in the New Labour government, said he took a “one-off decision” to vote for the Lib Dems in the recent European Parliament elections.