Burberry's offer to give the factory it is closing at Treorchy in the Rhondda to the local community has been met with strong criticism.
Workers took their protest to London again on Saturday
The clothing firm which is moving production overseas is guaranteeing £1m either to keep the plant as a going concern or to redevelop the empty site.
But campaigners and politicians have dismissed the offer as a PR stunt.
Around 80 workers from the Rhondda travelled to London to protest outside Burberry's flagship store on Saturday.
The Treorchy plant is due to close in March with the loss of 300 jobs six months after the company first announced it was to move production overseas.
Friday's offer by the international clothing company to underwrite the factory and its assets to the tune of £1m has not been warmly received .
Unions said they did not want an empty factory, Welsh Secretary Peter Hain said they had to make sure the factory was indeed an asset, and not a liability to the local community while the assembly government's enterprise minister said the offer was "wholly inadequate".
Campaigners, who want the firm to commit not to transfer production of the plant's polo shirts abroad, travelled to demonstrate outside the New Bond Street store in London for the second time in two months on Saturday.
Celebrities have backed the campaign for the factory to stay open
The company said it could not have made the offer before now because it would have prejudiced the consultation period.
Stacey Cartwright, its chief financial officer, said: "We are in the unenviable position of having had to take a very difficult commercial decision
"In the way in which Burberry operates on the global stage we have to remain competitive to ensure the longevity of Burberry as a very strong British brand.
"The most important priority for us right now having taken this decision is to now look after the employees , look after the community."
Burberry has emphasised that it does not intend to abandon the UK and it has offered Welsh staff jobs at its Yorkshire plant.
But Ms Cartwright said the company would not offer any contract to workers if they took over the site as a co-operative, for which a plan has already been put forward.
Enterprise minister Andrew Davies said he understood that it would take "very substantial investment" to upgrade the factory so it would be ready for another company.
Rhondda AM Leighton Andrews said the £1m offer would no make difference to the anti-closure campaign.
"If Burberry think people are going to be assuaged by this offer today they remain I'm afraid very much mistaken."
He said while talks about a possible co-operative working on the site were still going on, that would not provide jobs for the majority of the Burberry workers now facing redundancy in the Rhondda.
He was joined in condemning the offer by Plaid Cymru MEP Jill Evans. She said: "This is a small gesture which does not even come close to keeping 311 jobs for present and future generations in the Rhondda."
A strong anti-closure campaign has recruited celebrities as diverse as opera singer Bryn Terfel and Man United football coach Sir Alex Ferguson.