On Friday I went to Merseyside to visit the constituency of Angela Eagle, the former shadow defence secretary and shadow business secretary who is now a potential Labour leadership contender. Many Labour MPs returning to their constituencies this weekend, including Eagle, face a backlash from pro-Jeremy Corbyn party members incensed by moves to oust him from office.

The mood among these grassroots groups is hardening. They are urging activists to make their views known to their MPs at weekly surgery meetings, and promise a torrid time for MPs when they appear before their constituency Labour party (CLP) meetings in the weeks ahead. Eagle is in danger of becoming the focal point for this rage if she presses ahead with her challenge to Corbyn.

Eagle’s CLP in Wallasey – a once-bustling area on the other side of the Mersey from Liverpool, fuelled by the wages of dockers but now suffering from decades of unemployment and neglect – voted against any attempt to remove Corbyn a week ago. The office-bearers then wrote to Eagle to relay this message. But she ignored them. And they are incensed.

Liverpool and Merseyside, long bastions of the Labour movement, were at the heart of the civil war in the 1980s when the city was synonymous with the entryist group Militant. And Labour finds itself now on the brink of another civil war, one that could end with the party irrevocably split. That war may already be unstoppable unless Corbyn stands aside or the MPs hostile to him back off.

I went to Wallasey to talk to CLP members. She is seen as a good constituency MP, though there is unease about her backing for the 2003 Iraq invasion. Her proposed challenge threatens to create a chasm between her and party members. The Wallasey vote last week was 40 in favour of Corbyn, none against, and four abstentions. The judgement of Liam Hertzenberg, one of the members, is uncompromising. “I do not think she has the support of the CLP,” he said. “I hope she will be deselected.”

Corbyn last year ruled out mandatory deselection, two words guaranteed to create terror among MPs. But members, unhappy with the events of the past week, are actively discussing deselection, arguing it is time the parliamentary Labour party more closely mirrored the views of the constituency parties.

Hertzenberg, a 25-year-old self-employed digital and graphic designer, said he has written to Eagle this week. He expressed his unhappiness that she backed the no confidence motion in Corbyn, and plans to visit her surgery to make his point in person. She can expect to find the next meeting of her CLP uncomfortable, he predicts.

Paul Davies, vice-chair of the Wallasey CLP and a retired union official with Unite, shares the anger of Hertzenberg at the PLP’s behaviour. But the 64-year-old said that CLP officials had not mentioned deselection and, in spite of deploring the actions of the PLP, he defended Eagle’s democratic right to challenge Corbyn. Davies voted Corbyn last time and intends to again.

Support for Corbyn on Merseyside is, however, far from universally enthusiastic. When they are out knocking on doors, Labour councillors, who control 80 of 90 seats on Liverpool city council, say that a regular refrain is that Corbyn cannot win a general election.

Young Labour members also express disappointment at the lack of enthusiasm with whichCorbyn campaigned for remain in the European referendum. But these reservations seem to be outweighed by anger at the way the PLP has behaved.

Those organising against Corbyn, many from the Blair era, have established an online petition pressing him to resign – and are encouraging people to sign up for membership in preparation for a contest. Sixty thousand new members are reported to have joined in the last week. But that does not mean 60,000 are signing up to vote for a Corbyn alternative. The evidence in Wallasey is that at least some are signing up to support the current leader.

One of that number, Fiona Kelly, a teacher from Wallasey, joined the Young Socialists – Labour’s youth wing – aged 15 but left the party during the Blair years. She almost rejoined when Corbyn was elected but, now 47, has finally done so in order to vote for him. Kelly expressed frustration with the PLP for launching a coup attempt now. “I have waited a lifetime for this: when the Conservatives are in disarray,” she said. “Another chance might not come again. This should have been Labour’s moment.”

Corbyn has the support of both the unions, including Unite and the GMB, and of Momentum, the grassroots organisation set up last autumn to support him.

In my last article I wrote about the Merseyside branch of Momentum, which held an emergency meeting in the centre of Liverpool on Tuesday evening. It was planning a demonstration in support of Corbyn in the city centre on Saturday.

Unhappiness was voiced at the meeting with Eagle. But others saw the battle ahead as about more than just individual MPs.

There is a danger of a lot of casualties along the way: not only MPs such as Eagle but the Labour party itself.