George Osborne has said the test for approving Pfizer's bid for AstraZeneca will be whether it is in the UK's "national economic interest".
There have been concerns that a Pfizer takeover would result in a reduction in jobs and a hollowing out of the UK's science capability.
The Chancellor insisted "good British jobs" and "good British science" would be at the heart of the Government's thinking on the issue.
He also said it was "extraordinary" that Labour leader Ed Miliband had apparently turned down an offer to meet Pfizer's chief executive, Ian Read.
Mr Miliband has subsequently said he would be "happy" to meet with Pfizer's representatives.