* New head of UK's largest union warns of protest strikes
* Seeks to build alliance to fight state spending cuts
By Keith Weir
LONDON, Nov 24 (Reuters) - The new head of Britain's largest trade union warned the government on Wednesday that strikes were inevitable over state spending cuts and job losses, saying that anger was building across the country.
Former Liverpool dock worker Len McCluskey easily defeated three rival candidates to become general secretary of Unite, which was formed from the merger of two large unions, the TGWU and Amicus, in 2007 and has some 1.5 million members.
"Unite will support any of its members that wish to take industrial action to save the one and a half million jobs minimum that are currently threatened both in the public and private sector," McCluskey told reporters.
"I believe that such action will prove inevitable."
The Conservative-Liberal Democrat coalition plans to cut spending by 81 billion pounds ($128 billion) over the next four years to rein in a deficit running at more than 10 percent of national output.
McCluskey said that cabin crew working for British Airways could go on strike again after stoppages costing the airline 150 million pounds. Staff on London's Underground rail network plan to walk out again on Monday, bringing more disruption to the capital.
McCluskey, a left-winger whose union helps to bankroll the opposition Labour Party, accused the government of trying to destroy the welfare state, while protecting wealthy bankers.
"There is an incredible sense of anger that is beginning to build up and that anger can explode and manifest itself in all kinds of different ways at any time," McCluskey said, calling for groups opposed to cuts to join forces.
Demonstrators scuffled with police in central London on Wednesday when thousands of students and school pupils protested across Britain against government plans to raise university tuition fees.
CAMERON ATTACK
Workers in Portugal held a general strike on Wednesday to protest over austerity and there have also been protests in France and Greece.
McCluskey refused to rule out joining any wider pan-European protests but noted that Britain had tougher anti-union legislation than neighbouring countries, the legacy of Margaret Thatcher's rule in the 1980s.
Prime Minister David Cameron criticised McCluskey on Wednesday during the weekly prime minister's questions.
Cameron picked up on comments McCluskey had made in support of strikes and highlighted his links to a left-wing group that played a role in running the city of Liverpool in the 1980s.
"I think he's completely and utterly wrong and I think the world is in a slightly mad place where someone who supports militant tendency can get elected to the largest union in the country on 17 percent of the vote," Cameron said.
McCluskey dismissed attempts to portray him as an extremist.
"I've never called myself Red Len except when I'm supporting Liverpool Football Club," he joked. (Editing by Myra MacDonald)