The leader of Labour’s 6,600-strong army of councillors has delivered a stinging critique of the national party and its disastrous general election performance, accusing Jeremy Corbyn and his team of being out of touch with grassroots issues.

Cllr Nick Forbes, the leader of the Local Government Association (LGA) Labour Group, said there was a “huge sense of anger” among councillors – collectively the party’s second biggest funder, contributing £2m a year to party coffers – that they had been sidelined by the national leadership.

He accused the party hierarchy of ignoring warnings from grassroots councillors after last year’s disappointing council elections that issues with Corbyn and policy meant the party was failing to cut through to Labour voters on the doorsteps.

Forbes told the Guardian a “centralising, statist” party leadership had repeatedly disregarded local councillors’ experience and everyday connection with ordinary members of the public. “The party does not really take us seriously or involve us,” he said.

Forbes, who is the leader of Newcastle city council, accused the party hierarchy of “institutionalised councillor-phobia” and called for councillor representatives to be given a bigger say in party decision-making, including being allocated more seats on its ruling executive committee.

“The Labour party can continue into irrelevance or think deeply about what it is for in the 21st century. The local government community in Labour has to be part of the narrative of the rebalancing of the Labour party,” he said.

Forbes, interviewed before the party’s local government conference this weekend, released the findings of LGA Labour’s councillor survey, which found nearly three-quarters of respondents said Labour’s national leadership was the main reason for voters switching away from the party at the election. About 23% said Brexit was the main reason.

Just 12% of respondents thought the manifesto was a vote-winner, half said it was hard to sell overall and 37% said it was “a vote-loser – idealistic but unrealistic”. More than half said there should have been instead a greater focus on social care, while nearly half wanted more emphasis on crime and anti-social behaviour.

Dissatisfaction with the national party leadership among councillors is reflected in the survey findings that 86% felt undervalued by the party hierarchy, and 65% felt central support for local parties during council elections had been not very good or poor.

Asked what they thought were the most important lessons that national politicians could learn from local councillors, 61% said “connecting with voters” and 35% said “campaigning and winning elections”.

Forbes said councillors were collectively the party’s biggest funder after the Unite union, thanks to a compulsory levy on councillor allowances. The survey found 30% of councillors were prepared to refuse to hand over the levy if the party leadership failed to improve its relationship with local government.

Responding, a Labour party spokesperson said: “The Labour party highly values the work of our councillors. They tirelessly defend and promote the interests of their communities, despite suffering a decade of Conservative cuts. Councils have had 60p out of every £1 of their funding cut by the Tories. In the face of this, Labour councillors show day in, day out how we can translate our values into action.”

Forbes’s comments reflect longstanding councillor frustrations – stretching back beyond Corbyn’s leadership – that the views of locally elected members carry relatively little weight in the party, despite their practical experience in governing many of the UK’s biggest cities and towns.

The survey got responses from 822 out of 6,600 councillors contacted online between 17 and 31 January. The majority of respondents had been Labour party members for more than 10 years and councillors for more than six. Nearly one in 10 were council or local group leaders, while 40% were backbenchers.

Forbes described local councillors as the “backbone of the party who fly the flag for Labour in desperate circumstances”. They spent an average of three hours campaigning for Labour every week, he said, collectively helping an estimated 1.5 million people with their problems each year.

“Councillors deal with people’s problems all hours of the day and night. They know what is on people’s minds, what is troubling them and what makes them tick. We are accountable to our communities. We have to look our constituents in the eye and they are not shy about asking tough questions.”

One senior councillor told the Guardian the survey findings reflected tensions in the party that have emerged since 2015 between a minority of newer leftwing members who regard Labour in local government as part of an “ancient regime”. He said: “A lot of the senior councillors I speak to would say the survey results ring true. But how far this is them having a view and then finding evidence to back it up I don’t know.”

Labour councillors lead 130 out of 397 councils in England, Scotland and Wales, including Birmingham, Manchester, Liverpool, Sheffield, Leeds and Bristol as well as 20 London boroughs.