The leader of Britain's biggest union is calling on millions of working people to prepare for a national campaign of "civil disobedience" and co-ordinated strikes in protest at coalition cuts to pensions and public services.

In a rallying cry ahead of the Trades Union Congress, which opens in London on Sunday, Len McCluskey, general secretary of Unite, warns that the movement will head into "terminal decline" if the UK's 6.5 million union members fail to "stand up and fight" this autumn.

In terms that will alarm the Labour leader, Ed Miliband, who won the leadership a year ago on the back of union votes and has worked since to shed his "red Ed" label, McCluskey says all forms of organised action and disruption should be considered to defeat a government with "no legitimacy".

"My view is that we should rule nothing in and nothing out. Every conceivable form of protest and action should be carefully considered, from civil disobedience through to co-ordinated industrial strikes," he said in an interview with the Observer. "Everything should be considered in the face of the type of onslaught that we are looking at."

McCluskey, who condemned last month's riots and looting as "the exact opposite of community spirit, collectivism and what trade unionism is all about", said non-violent civil disobedience would be justified. "The reality is that we have got to demonstrate to people that unions are organisations that we are proud to belong to. If we don't – if we run for cover – if we involve ourselves in shabby compromises and shabby deals, if we appear frightened in the face of the enemy, then who would want you on their side?"

He added: "The concept of protest is as old as democracy itself. We should looks at all forms of engagement. That is why we are involved in a coalition of resistance with church groups, with community organisations, with student organisations, with unemployed organisations, with senior citizens organisations, creating people power that can demonstrate its anger against a coalition that we don't believe has a mandate to do what it is doing and to try to persuade it to take a step back."

Unite, which has 1.55m members, is expected to announce details this week of plans to ballot them on strike action, as is Unison, the public services union, and the GMB general union. On Friday, the NASUWT teaching union announced a ballot that it said could lead to strike action by up to 250,000 school staff.

Its general secretary, Chris Keates, said ministers were riding roughshod over measures to support teachers and raise standards. In June, the National Union of Teachers and the Association of Teachers and Lecturers took part in a one-day strike over cuts to pensions.

Government plans to increase the amount that public sector workers pay into pensions by an average 3%, while at the same time raising the pension age, are likely to dominate the TUC.

McCluskey, whose union is Labour's principle donor, said he did not expect Miliband to back him on strikes or civil disobedience. "I would like him to support our campaign but I don't expect him to … I suspect he is worried about the union tag that the media put on him."

The Unite leader said talks with ministers on pensions had made minimal progress, making it almost certain that there would at least one co-ordinated one-day strike across the public services before the end of the year. This is expected to be followed by a rolling programme of targeted action and so-called "smart strikes" involving selected groups of workers. "I think, therefore, it is almost inevitable that there will be large-scale industrial action within the public services before the year is out."

A former Liverpool docker, McCluskey cited the poll tax riots that helped bring down Margaret Thatcher, the protests against the Iraq war that hardened opposition to Tony Blair and the "Arab spring" pro-democracy uprisings as evidence of where "people power" can make a real difference.

Last night the unions appeared to be backing away from a confrontation with Miliband over his plans to reduce the union vote at Labour's conference. The Labour leader, who is addressing the TUC on Tuesday, has indicated he wants to loosen the grip of union leaders over party policymaking. McCluskey said he had an "open mind" about the ideas and did not expect a big row about them.

In his opening speech, the TUC general secretary, Brendan Barber, will call for reform of banks. Ahead of the release this week of a report by the government's commission on banking reform, he will say: "Banking should be a utility just like energy and water, supplying credit and the other services that our productive industries and services need. The spectre of a double dip is raising its head. We desperately need an economic stimulus.

"Unless we move to a low-carbon economy, we face climate chaos. The real challenge, therefore, is how to raise investment – not just by companies but in infrastructure and the public works that can provide jobs, restore confidence and kickstart growth.

"And while the political classes seem rather embarrassed and can't wait to get rid of them, the public has big stakes in two major banks. It's time we put them to work on behalf of the public."