President Thein Sein resigned on Thursday as chairman of the leading Union Solidarity and Development Party (USDP) and will be replaced by his political rival and party vice-chairman Shwe Mann, according to the Union Daily.

Thein Sein is technically barred from taking part in “party activities” during his term of office under Burma’s 2008 constitution, but has continued to lead the USDP since becoming president in March 2011. Despite mounting criticism over his dual role, Thein Sein was re-elected as party chairman in October last year.

Shwe Mann, who is also the speaker for the lower house of parliament, is set to replace the president in his former role, it was officially announced at the end of a three-day USDP youth congress on Wednesday.

Thein Sein and Shwe Mann have locked horns in the past – notably in a heated dispute over the role of Burma’s constitutional tribunal last year – and are described by many analysts as political adversaries. Shwe Mann has been identified as one of the potential candidates to replace Thein Sein as president in 2015, if the USDP were to win the next general election.

According to a report in Xinhua, Shwe Mann highlighted the importance of safeguarding Burma’s “multi-party democratic system” and “market-oriented economic system” as reasons behind the resignation. He has previously criticised Thein Sein for dragging his feet on the pace of democratic  reforms in the former pariah state.

Thein Sein formed the military-backed USDP in April 2010 in order to run in the November election, which the party won by a landslide amid widespread reports of electoral fraud. Aung San Suu Kyi’s National League for Democracy famously boycotted the elections.

The USDP is estimated to have over 4 million supporters nation-wide and is dominated by former generals from the military junta. The party paper, the Union Daily, was one of the first publications to be granted permission to start printing on a daily basis on 1 April.