Momentum and trade unions are set to force a vote on strikes and pay increases at the Labour conference, with motions designed to contradict Keir Starmer’s stance. The campaign to win support for the motion will be launched this week by the former shadow minister Sam Tarry, who was sacked for joining a picket line and contradicting Labour policy on pay in broadcast interviews. Momentum will launch its campaign on Thursday with Tarry and fellow Labour MPs Dawn Butler and Jon Trickett, as well as Andrea Egan, the president of the trade union Unison. The motion will echo Tarry’s backing for workers demanding pay increases in line with inflation – the line Labour sources said had contradicted Labour policy. Tarry said Labour should take the opportunity at conference to show solidarity with striking workers. “Labour has a huge chance to show it’s on the side of working people,” he said. “But by firing shadow ministers like myself for standing on picket lines, Keir Starmer is in danger of driving a wedge between Labour and the millions of working people desperate for real relief in this escalating cost of living crisis. I am proud of our party’s historic links to the trade unions – it’s time all of our party were.” Starmer has told his frontbenchers that the party should not join picket lines and instead should focus on calling out the government to end the disputes. This week, the shadow chancellor, Rachel Reeves, reiterated the party’s position, which has come under fire from its own MPs. Lisa Nandy, the shadow levelling up secretary, caused a rift in the shadow cabinet when she joined striking members of the Communication Workers Union in her constituency. The stance is likely to come under further pressure this week with another series of transport strikes by the RMT on rail and underground networks. Momentum will ask local parties to submit motions for conference that say Labour MPs have rights to stand with striking workers on picket lines, that Labour backs an “inflation-proof pay rise” as well as public ownership of utilities and the abolition of anti-trade union laws. Many constituency Labour parties had already submitted motions to conference before the launch of the Momentum campaign, and more are expected to do so in September. However, sources in the campaign said the motion was expected to get widespread union backing, which increases its chances of being debated on the conference floor. The proposed motion will say supporting workers on picket lines “sends a strong message about what workers can expect of a future Labour government” and calls for the party to “oppose real-terms pay cuts for workers and to support wage rises in line with and in excess of the current inflation level”. It also calls on the party to “commit to increasing taxes on corporate profits to bring inflation down” and for Labour MPs and frontbenchers to “show solidarity with striking workers by attending picket lines and vocally supporting strikes”. Any motion finally put to conference is likely to be subject to negotiations to propose an acceptable composite. Hilary Schan, a co-chair of Momentum, said: “Despite the lack of leadership from the top, the labour movement stands united. Over the coming weeks, Momentum activists will use every lever at our disposal to ensure our party fulfils its historic mission: for Labour to stand with labour.” Manuel Cortes, the general secretary of the Transport Salaried Staffs’ Association, said the union welcomed the campaign. “Britain urgently needs a pay rise, a cap on prices and profits and public ownership of utilities,” he said. “That’s why no ifs, no buts, Labour must support workers on strike demanding fair wage increases which keep pace with inflation.” Momentum insiders concede there are likely to be far fewer leftwing conference delegates voting on behalf of Labour members at this year’s conference, giving the leadership an advantage in weeding out unpopular motions. The change is down to a significant number of backers of the former leader Jeremy Corbyn leaving the party and more centrist members organising to win more internal local party elections for key positions. The relationship between Starmer and some unions has deteriorated over the last year, particularly with Unite, led by Sharon Graham. The Rail, Maritime and Transport Workers union, whose members will strike this week, are not affiliated to Labour. One Labour source suggested the party had been vindicated in its decision to ask MPs to keep their distance from the RMT strikes, citing the potential backlash against the party after the RMT leader, Mick Lynch, voiced scepticism about Russia’s invasion of Ukraine in an interview. He said the “EU also provoked a lot of the trouble in Ukraine” during the 2014 revolution, suggesting it was “not just that this stuff has sprung from one place”.