* President Thein Sein sacked ruling party chief on Wednesday
* Shwe Mann made "questionable" decisions in parliament - minister
* Ruling party worried about his ties to rival leaders - minister
* No turning back on reform process - minister
* Security forces surrounded party's headquarters on Wednesday
By Hnin Yadana Zaw and Antoni Slodkowski
NAYPYIDAW, Aug 15 (Reuters) - Myanmar President Thein Sein sacked Shwe Mann as ruling party chairman this week because he supported controversial bills in parliament and had ties to rival party leaders, the information minister told Reuters in an interview on Saturday.
The comments by Ye Htut, who is also Thein Sein's spokesman, are the most detailed yet by the government on why Shwe Mann was ousted just three months before a general election.
The battle between two of Myanmar's most powerful figures played out in dramatic fashion on Wednesday when security forces surrounded the headquarters of the Union Solidarity and Development Party (USDP) in the capital Naypyitaw.
Shwe Mann had antagonised the military by building ties with Nobel laureate Aung San Suu Kyi and backing her campaign to change the constitution. The military handed power to a semi-civilian government in 2011 but retains an effective veto over changes to the political system.
Both Thein Sein and Shwe Mann are former generals who played prominent roles in the junta that ruled Myanmar for 49 years.
Members of the USDP's governing body sent Thein Sein a secret letter a few weeks ago to express concerns about party policy under Shwe Mann, Ye Htut said.
They were also concerned about a lack of transparency in his relationships with rival party leaders, he said, although he declined to say with whom.
While acknowledging Shwe Mann's ouster was not good for the party's image ahead of the November election, Ye Htut said Shwe Mann had made some "very questionable" decisions in parliament over the past year that reflected his own political ambitions rather than what was best for the party and the country.
That included his support in June for a constitutional amendment to limit the military's power, a bill that failed to pass parliament but was backed by Suu Kyi, he said.
"He sometimes tried to force his will on other people," Ye Htut said. "This kind of thing happened again and again. Because of his leadership style, there was a lot of concern about inter-party democracy."
Efforts by Reuters to reach Shwe Mann on Saturday for comment were unsuccessful.
In his only public comment since being ousted, Shwe Mann said in a post on his Facebook page on Friday that he would "work for the good of the people and will stand for the people until the end".
He still holds the powerful post of speaker of parliament in Myanmar's lower house, and on Friday he visited the parliamentary complex.
REFORM CONTINUES - MINISTER
On Wednesday, Thein Sein informed the USDP governing body that one of his allies, Htay Oo, was the new party leader, Ye Htut said.
Shortly afterwards, security forces surrounded the party's headquarters.
The United States has expressed concern about the use of security forces to resolve the dispute.
Ye Htut said the handling of the matter would have no bearing on the pace of reform in Myanmar.
"There is no turning back in the reform process," he said. "This is not good for the image of the USDP coming so close to the elections ... this is an internal dispute and will not affect the executive."
Washington's concern about reform was unwarranted, he added.
"Sometimes, I'm surprised about the concerns from the political circle in Washington," he said. The country needed free and fair elections to be able to move ahead with reforms, he added.
Suu Kyi's National League for Democracy (NLD) is expected to beat the USDP in the ballot.
The military-drafted constitution bars the Oxford-educated Suu Kyi from becoming president because her two sons are British, but a strong NLD performance will increase her influence over the choice of the next president.
Reuters reported last year that the NLD might back Shwe Mann as a presidential candidate after the election. (Writing by Simon Webb; Editing by Dean Yates)
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