An arts centre used by tens of thousands of residents faces closure after culture chiefs announced plans to axe funding from next year.
Watermans, in Brentford High Street, runs scores of projects for vulnerable people, including the largest club for people with learning disabilities in Europe, as well as hosting films and theatre.
But the Arts Council, which is responsible for handing out public money for culture venues, last month decided to cut nearly £500,000 in annual funding for the riverside facility.
Catriona Macrae-Gibson, head of communications at the Arts Council, said it had taken the decision due to 'very serious concerns' over the running of the centre and its 'poor performance' in key areas.
"We have worked very closely with Watermans over a number of years but there came a point when the investment of public money needed to come to an end," she added.
"This is entirely to do with the business plan failing and the poor management and viability of projects."
Watermans chiefs claim the decision was "a bolt out of the blue" and have hit back at the charges.
Marketing director Leigh Stops said: "We have been doing very well recently, organising lots of small projects that are vital for the community."
Centre staff also point to a 50 per cent increase in cinema, theatre and exhibition audiences in recent years and argue they have met targets for securing additional external funding.
Mr Stops, who is co-ordinating a petition against the cut, claimed the move will hit the most needy hardest.
"It's not just Watermans that will suffer but the whole community. People with mental health issues through to disaffected teenagers will lose out," he said.
The director believes the timing of the announcement - just weeks before Christmas - was also significant.
"A letter from the Arts Council suddenly came through in December, leaving us limited time to appeal by mid-January. It seems big institutions have had their grants increased and, to pay for that, smaller grants have been cut with no warning.
"They hope the small guys will go quietly."
The Arts Council conceded the timing was 'far from ideal' but insisted it was caused by a year-long delay in finalising its own funding settlement from the Treasury.
Brentford & Isleworth MP Ann Keen and the three ward councillors have all backed the campaign, which by last week had gathered more than 1,000 signatures.
Too find out more about how to support the centre and what is coming up visit the Watermans website