The Sirisena and Rajapaksa factions have united to face arch rival United National Party (UNP), senior United People's Freedom Alliance (UPFA) leader Anura Yapa said.
Sirisena has for long resisted his predecessor's re-entry into politics after his shock victory as the opposition unity candidate in the January 8 presidential poll that ended Rajapaksa's decade-long rule.
The president's decision to allow Rajapaksa back has shocked many in his coalition.
One of the coalition partners, the Buddhist nationalist JHU has already left the UPFA while other parties such as the Marxist JVP has directly accused Sirisena of betraying the January mandate.
As someone who was critical of excesses during Rajapaksa's rule, alleging abuse of power, curtailing of civil freedoms and human rights in the run upto the January polls, Sirisena appears to have succumbed to pressure from his predecessor's loyalists who ran a nationwide campaign to have the former president back in the UPFA.
