Jeremy Corbyn announced a new body to improve workers' rights as he addressed the largest ever May Day rally in London.

The Labour leader joined hundreds of people at Clerkenwell Green in the capital to mark international workers' day - the first time the head of the party has addressed the rally in 50 years.

He told the crowds that the Government's trade union legislation would "reduce the ability" of organisations to "speak up for people during election campaigns".

Mr Corbyn announced a new commission to tackle workers' rights and zero hours contracts.

"We will be establishing, in a couple of weeks time, an organisation or a commission called 'Workplace 2020' which will be looking at the end to change or improve trade union and workers' rights, including self employed workers."

He said the initiative would "end the scandal of zero hours contracts", "end the scandal of insecurity" and "end the scandal of a lower wage for younger workers when their needs and demands are just as great as any older worker - to end their discrimination".

Mr Corbyn continued: "And to say to those fast food chains and others that think you can evade the idea that trade unions have a right to organise.

"We want there to be a positive right to join and be represented by a trade union in every workplace in our country."

Hundreds of people marched through the streets of London from Clerkenwell Green to Trafalgar Square carrying placards with slogans supporting junior doctors, human rights and calling for David Cameron to resign.

At one point the rally was stalled as it passed along the Strand where a group of protesters from the Unite union, campaigning against the Melia hotel group, set off red smoke flares.

Frances O'Grady, general secretary of the TUC, wished the crowd a happy May Day and sent a special message of solidarity to BHS workers.

She said: "We stand by you."

General secretary of the National Union of Teachers (NUT) Christine Blower addressed the rally at Trafalgar Square and said that the union would ballot for strike action before the summer holidays.

She said: "In education we are facing onslaught after onslaught of what should be a civil right and a public good. That is education.

"Instead we are facing privatisation and the destruction of a coherent service.

"But we will in the National Union of Teachers... we will say 'no' to those things and we will be balloting for national strike action before the end of this term."

Junior doctor Yannis Gourtsoyannis also spoke at Trafalgar Square and said that the NHS would be the site of the last stand against austerity.

"Social democracy in the UK began with the inception of the NHS in 1948," Dr Gourtsoyannis claimed.

"So too will the NHS be the site of Britain's last stand against the all-consuming forces for austerity and so too will the NHS be a catalyst for a wider workers' movement to defend what is good about this country. He pleaded with the rally to not let the NHS fail and to defend the BMA.

"We need you and you need us," he said.

Mr Corbyn spoke about the junior doctors' strike during his speech in Clerkenwell, where he claimed that it was "beyond disgraceful" that the Health Secretary Jeremy Hunt was "more interested" in privatising 49% of NHS services than coming to an agreement with the health workers.

He said he was "proud" to march with the junior doctors through Westminster last week with the shadow chancellor John McDonnell, who attended a May Day rally in Glasgow on Sunday.

Mr Corbyn said the London rally had a long tradition of standing up for the "timeless principle" of uniting the working class.

He called to the crowd to "work to achieve a society where there isn't the grotesque levels of inequality that there are".

The rally celebrated "what was won by workers' campaigning over many years", including the NHS, education, pensions and affordable housing, which organisers claimed were under attack by the austerity agenda.