By Holly Williams, Press Association Deputy City Editor

Bookmaker Ladbrokes disclosed a 57% plunge in third quarter earnings after being hit by higher gaming taxes and costs of a major marketing push.

The group, which is waiting for regulatory clearance for a £2.3 billion mega-merger with rival Gala Coral, said UK revenues fell 0.7% in the three months to the end of September compared with a year earlier, when it was boosted by the football World Cup.

Stripping this out, revenues were 2% higher.

Ladbrokes posted underlying earnings of £14.3 million, less than half the £33 million seen a year earlier, but stressed this reflected investment in a turnaround plan launched earlier this year.

Jim Mullen, chief executive of Ladbrokes, said: "These numbers reflect the first 68 days of activity since we announced our organic plan to aggressively invest and grow our recreational and multi-channel customer base particularly across UK retail, Ladbrokes.com and Ladbrokes Australia.

"It is early in our journey, but today's results reflect positive initial progress."

The group has hiked spend on marketing campaigns in the UK, with a focus on television advertising, which is said had helped increase bets staked by 17.5% so far in the football season.

Overall, bets made in its 2,161-strong chain of bookies in the UK rose 1.6% - or 3.5% with shop closures stripped out - and Ladbrokes said the Rugby World Cup was better-than-expected for the group.

A number of football results went its way, although it saw a number of unfavourable horse racing results, particularly in September.

Online revenues continued to be the star performer, up 6.4% in the third quarter, or 10.5% excluding last year's football World Cup.

The group shut another eight shops under plans to close 60 throughout 2015.

Its merger with Gala Coral will form a gambling giant with more than 4,000 shops and will see it overtake the UK's biggest bookmaker William Hill.

The move will give it greater might in the face of new taxes and the need for greater investment in marketing and technology.

It comes amid a wave of consolidation in the sector, with Irish chain Paddy Bower and online gambling group Betfair also set to join forces in a £5 billion tie-up.

But Ladbrokes and privately-owned Gala Coral will first have to appease the Competition and Markets Authority (CMA) and are likely to have to sell shops to achieve the green light.

Ladbrokes said on releasing its latest update that the merger was "on track".

Mr Mullen added: "The CMA work is progressing but there is no material news that we can share on that today."

Shares rose 5% as the third quarter earnings drop came in line with expectations.

Analysts at Peel Hunt said the third quarter was "always going to be tough", but cheered "signs of encouragement" in the online and retail estate revenues.