Shelter employs 850 staff and helps 170,000 people annually in the UK

It follows a walkout on 5 March after Unite union members at the charity voted for industrial action.

They say the new contracts mean they will have to work an extra two and a half hours a week without more pay.

Shelter management says the changes will enable it to meet its obligations and plug a funding shortfall.

'Rights destroyed'

The new contract will also remove an employee's right to an annual incremental pay rise.

The charity says salary increases alone cost it more than �1m last year.

But the union says workers' rights are being destroyed.

Shelter says a third of its 850 staff took part in last week's strike.

Unite regional industrial organiser Alan Scott said: "We believe that the strike action - and the massive support it has had from both the general public and the people with whom Shelter works in tackling homelessness - has delivered a clear message to Shelter managers that it is time to negotiate reasonably with us."

Shelter spokesman Brendan Murphy says management's position is unchanged, despite the second day of action.

He said: "Seventy-five per cent of Shelter staff have accepted the new contracts and more are signing up every day.

"We expect everything to be resolved by 1 April when the new contracts start."

Film director Ken Loach is backing the strike, saying staff's concerns are justified. He is urging a boycott of Shelter.