The US private equity firm targeting a potential takeover of pub group Marston’s said it has now walked away from a deal.

Shares in Marston’s tumbled on Thursday morning after Platinum Equity Advisors said it will not make a firm offer after its 105p per share offer was rebuffed.

Last week, Marston’s said it believed that the £666 million bid “significantly undervalues” the pub and brewing business.

Platinum had previously approached the Wolverhampton-based firm with 88p and 95p per share offers in December.

It comes as all of Marston’s 1,368 pubs remain shut to customers due to the national coronavirus lockdown.

On Thursday, Marston’s said it believes it is “well placed” to benefit from potential growth opportunities after coronavirus restrictions are relaxed.

It told investors that it hopes to be buoyed by the increase in home-working, which will benefit pubs in suburban locations.

It added that it also expects to benefit from the acquisition of 156 Brains pubs in Wales it completed in December.

In a statement, the company said: “Marston’s has a strengthened balance sheet following the creation of the synergistic joint venture with Carlsberg and significant cash headroom, enabling it to continue to absorb the impact of the temporary Government restrictions.

“We welcome the continued nationwide rollout of the vaccine programme and look forward to rebuilding trading momentum once restrictions are lifted.”

During a challenging year, the business merged its brewing arm with Carlsberg UK, forming a joint venture worth around £780 million. Marston’s has a 40% stake in the business.

Shares in the company were 12.8% lower at 86.8p in early trading.