LONDON (Reuters) - National Grid (>> National Grid plc) has sold a majority stake in its gas network in a 5.4 billion pound deal which could test Prime Minister Theresa May's pledge to vet infrastructure sales to foreign buyers.

The FTSE 100-listed group said on Thursday that a consortium led by Australian investment bank Macquarie and which includes Chinese and Qatari state investors, had bought a 61 percent stake in the gas pipe arm, valued at a total 13.8 billion pounds, which serves nearly 11 million households and businesses across Britain.

Since taking office, May has been keen to state that Britain remains open for business following the vote to leave the EU. But she has also said the government should be able to step in to defend a key sector from foreign ownership.

May in September gave the go-ahead for the $24 billion (£18.90 billion) Hinkley Point C nuclear power plant after weeks of uncertainty over security concerns that had strained ties with China, which will help pay for it, and France, which will build it.

CIC Capital Corporation, a wholly-owned subsidiary of China's sovereign wealth fund, is part of the consortium buying the stake in National Grid's asset.

"CIC already have holdings in Heathrow Airport and Thames Water, they're well known in the UK infrastructure market today. There are absolutely no concerns," National Grid Chief Executive John Pettigrew told Reuters.

The deal comes just weeks after Britain's second-largest energy supplier SSE (>> SSE PLC) sold a minority stake in its own gas distribution network to Abu Dhabi Investment Authority for 621 million pounds.

National Grid said it will pay out most of the proceeds, or 4 billion pounds, to its shareholders. It will pay at least 75 percent of this in a special dividend in the second quarter of 2017, it said.

For the network operator the dilution of its British gas asset means its U.S. business grows in importance.

"The bigger point is that National Grid is rotating towards America, where it has previously highlighted it sees stronger growth," said Roshan Patel, utilities analyst at Investec.

Hermes Investment Management, which is one of the other consortium partners along with Allianz Capital Partners, Qatar Investment Authority, Dalmore Capital and Amber Infrastructure, said it was attracted to the investment for its high level of cash yield and inflation-linked revenues.

The parties said they had also agreed the consortium could buy an extra 14 percent stake in the gas distribution asset under broadly the same terms at a later stage.

Shares in National Grid shares were trading up 1 percent by 1100 GMT.

National Grid was advised by Morgan Stanley, Robey Warshaw, Barclays and Linklaters. RBC Capital Markets, Macquarie Capital and Clifford Chance advised the buyers.

(Additional reporting by Simon Jessop and Pamela Barbaglia; editing by Lina Saigol and Susan Thomas)

By Karolin Schaps and Susanna Twidale

Stocks treated in this article : SSE PLC, National Grid plc