Unison union members at Lambeth College have announced a two-day strike on Wednesday and Thursday of next week.
They will join workers in the UCU union, who began their second day of an all-out strike today, Wednesday.
Workers at the south London college are fighting new contracts that slash holiday, sick pay and impose longer working hours.
Unison's announcement makes a mockery of college principal Mark Silverman's desperate claims that support for the strike is waning.
Support has flooded in for the all-out strike. Silverman sent out his latest antagonising email to workers yesterday. It claimed only a minority were backing the action.
David, who was picketing in Brixton, told Socialist Worker, "The email said only a minority are striking. It's ridiculous. Instead of talking to us he just tries to impose his will."
David joined the UCU after workers struck on 1 May. Strikers say many workers have joined the union in the course of the dispute.
Strikers Mario and Brian spoke at a meeting of UCU members at London South Bank University today. Mario told the meeting, "UCU membership has increased enormously because people can see that collectively we can fight."
Brian said, "If we don't win, you will have the same contracts turning up here."
Workers collected £105 for strikers at the meeting. Another worker described how she had collected £45 in her department alone. And workers plan to collect a weekly levy from UCU members at LSBU in support of Lambeth strikers.
Carl is a UCU member at LSBU. "I'm fully in support of people on strike," he told Socialist Worker. "They are dedicated, committed workers who are seeing their terms and conditions eroded.
"This will impact on education and how students learn too."
Other strikers went to speak at the City of Westminster College. The diary of appointments for strikers to speak in union meetings is filling up fast.
One parent of a student at the Brixton site explained why she was backing the strike.
She said, "I worked for 19 years as a primary school teacher. Management don't understand why teachers and lecturers need holidays. You need the time to recover and recharge the batteries."
Johnny was picketing in Clapham. He said a handful of UCU members had gone into work there, but the strike was generally solid. "There's a propaganda war going on," he told Socialist Worker.
"Silverman is trying to convince people there are fewer people on strike than there actually are. But despite his dirty tricks, only a few union members have gone into work."
There are also some workers who still aren't in the union. Explaining the dispute to them and recruiting them to the union would make the action even stronger.
Ivan is a striker at the Vauxhall site. "All working people are living on quicksand," he told Socialist Worker. "But Tower Hamlets College workers had an indefinite strike a few years ago and they won. If you don't fight, how are you going to win? If you fight you might win, so we're fighting."
Show your support for this vital dispute
Workers have called for a solidarity picket at the Clapham site of Lambeth College for Friday morning from 7am and they will rally at 11am.
Every trade unionist who can get there should bring banners, collections and delegations to the picket line. This is an urgent dispute that will have ramifications for workers everywhere - and every bit of support makes a difference.
Visit picket lines from 7am every day in Brixton, Clapham and Vauxhall and a mass meeting each day at 11am at the Clapham site.
Organise collections or weekly levies to support the strike.
Invite strikers to speak in your union or campaign meeting and rush messages of support to email@example.com