The centre will be Amnesty's UK headquarters, and will be furnished with a 250-seat auditorium, a creative studio, media room and 'direct action' stations. Staff are expected to move in by the end of the year.
Some 60 per cent of the funding came from individual major donors, with the rest coming from trusts and foundations, said Carol McCormack, Amnesty's capital appeals director.
"We really had to shake up our donor relations when we started this appeal," she said. "We are trying not to impact on our current revenue streams, although we did have the most successful appeal to our membership ever."
A single appeal to Amnesty's 60,000 UK members, with two direct mail-shots, raised £400,000 towards the new centre.
Currently, the organisation has two offices and is "bursting at the seams," said McCormack. "We wanted a centre to reflect our ambitions for the future.
I think our supporters and members understand the need for this.
"It shows that this is about our activists and members and is very much focused on young people. The basic idea of the action centre is to create a human-rights culture in the UK.
"Members are not questioning it because it is about increasing our campaigning capacity, our resources and facilities."
- A group of "pilgrims for peace" comprising people of various religions including Christians, Muslims and Jews, are undertaking a 500-mile journey of understanding to raise funds for Amnesty International in the first week of June.
The Road 4 Peace will follow the medieval pilgrimage route starting in Port-de Pied in France and ending in Santiago de Campostela in northern Spain. Forums will be held along the way to discuss politics, religion and philosophy.