WASHINGTON (Reuters) - T-Mobile US TMUS.O said it is getting advice on its proposed $26 billion merger with Sprint Corp S.N from a lobbying firm whose staff includes several members of President Donald Trump's election team such as former campaign manager Corey Lewandowski.

Former Trump campaign manager Corey Lewandowski departs after appearing before the House Intelligence Committee on Capitol Hill in Washington, U.S., March 8, 2018. REUTERS/Joshua Roberts

Lewandowski is among those advising the No. 3 wireless company on its deal as it bolsters its defenses ahead of a what will likely be a tough regulatory review process, T-Mobile said in a statement last week.

T-Mobile US agreed in April to buy Sprint in an $26 billion, all-stock deal that will combine the third and fourth largest U.S. wireless carriers.

Lobbying disclosure reports show T-Mobile has paid Turnberry Solutions LLC $100,000 since September 2017. T-Mobile told Reuters last week that work by Turnberry included advice on its merger with Sprint.

T-Mobile added that Lewandowski “is now affiliated with (Turnberry) and they have offered perspective to T-Mobile on a variety of topics, including the pending transaction.”

According to lobbying disclosure forms filed with the U.S. Senate on April 20, Turnberry said it was providing “guidance and counsel on telecommunication issues” and had lobbied White House staff, among other agencies.

Among those lobbying on T-Mobile’s behalf from Turnberry include Mike Rubino, who oversaw Trump’s campaign in several states, Jason Osborne, a former senior adviser to the Trump campaign and Ryan O’Dwyer, a former Trump campaign aide, the disclosure report said.

T-Mobile said it hired Turnberry in August. In early August, Bloomberg News reported the company had resumed talks with Sprint about a potential merger. The companies in November said they had called off the talks and later resumed them.

Lewandowski, who was Trump’s first campaign manager, took on a role with Vice President Mike Pence’s leadership political action committee last month.

Lewandowski did not respond to a request for comment.

Lewandowski has worked as a lobbyist and a political consultant after a nearly six month stint leading the Trump campaign in 2016.

The Federal Communications Commission must determine if the merger is in the public interest, while the Justice Department must determine if the merger would harm competition.