Flutter Entertainment has received unconditional phase one clearance from the UK Competition and Markets Authority for its proposed deal with The Stars Group.
Paddy Power owner Flutter agreed last October to buy the Canadian group in a $6 billion share deal set to create the world's largest online betting and gambling company by revenue.
The proposed transaction is still subject to approval by Flutter shareholders at its extraordinary general meeting and by The Stars Group shareholders in April.
It also remains conditional on approval from a small number of other regulatory bodies, some of whom have indicated that their usual timeframes may be delayed by the current Covid-19 crisis.
Peter Jackson, Flutter Entertainment's chief executive, said the announcement from the CMA marks a further important milestone in the process towards completion of the proposed combination with The Stars Group.
"We continue to work with the remaining international regulatory authorities to obtain the last of the outstanding approvals," he added.
Mr Jackson said last week that in these "challenging times", he was more convinced than ever of the strategic fit of the two complementary businesses.
He will retain his role in the combined group.
When the deal was announced, the two companies said their combined annual revenues would have totalled £3.8 billion in 2018, making it the largest online betting and gaming operator globally.
The merger is expected to deliver pretax cost synergies of £140m a year, along with opportunities to cross-sell products to one another's customers in international markets and lower finance costs, they said.
Shares in Flutter soared in Dublin trade today.