The UK is set to change its rules on corporate takeovers to make it harder for hostile bids to succeed.

Bidding companies will also have to disclose more about what they plan to do with the target company’s assets and its employees. And they will have to stick to any promises they make for at least a year.

The "put-up-or-shut-up" deadline will also be shortened – buyers will be required to put a formal bid on the table within four weeks of showing an interest, or walk away.

The Panel of Takeovers and Mergers, which enforces the country’s rules on listed company takeovers, said it had become too easy for hostile bids to succeed and for short-term investors to influence the outcome of a bid.

It said some bidders had used its rules to “obtain a tactical advantage” over their targets and its proposed rule changes would “redress the balance in favor of the offeree company”.

The move to hold companies accountable for any promises they make during a bid follows US food group Kraft’s hostile takeover of confectioner Cadbury in 2009.

Kraft said it would keep certain Cadbury factories open, but then announced their closure once the deal was completed.