Britain should conduct an independent assessment of a potential takeover of British pharmaceutical firm AstraZeneca by US drug maker Pfizer, Reuters reported on Sunday, citing opposition Labor party leader Ed Miliband.

AstraZeneca rejected a 63 billion pound ($106 billion) takeover bid from Pfizer on Friday, but the US firm is expected to pursue its interest.

"We need a more substantive assessment of whether this takeover is in the national economic interest before the UK government allows itself to be seen to be supporting it," Miliband said in a letter to Prime Minister David Cameron.

The government has said it has no intention of intervening in the deal and considers it a matter for shareholders.

But ministers have been pressing Pfizer for assurances over jobs and continued investment in facilities in Britain.

Pfizer wrote to Cameron on Friday pledging to retain British jobs and a planned scientific research hub in Cambridge.

Pfizer said on Friday it was determined to reach a deal that would restore its status as the world's biggest pharmaceutical company despite AstraZeneca's rejection of its latest cash and stock offer.

The move could jeopardize the jobs for employees at Pfizer Inc's US research centers, Reuters reported over the weekend.

To reassure the British government about its proposal, Pfizer has promised the combined company would keep 20 percent of its research and development workforce in the UK.