According to Section 245 (1) of the charter, ombudsmen were not empowered to ask the court to consider the constitutionality of an election, the party said in a statement.
Section 245 (1) provides the ombudsmen may submit a case to the Constitutional Court "if the provisions of any law beg the question of constitutionality".
Since an election is not a law, the ombudsmen could not challenge its legality, the party maintains.
By the same token, it said, the court breached the constitution when it accepted the case because nothing in the charter allows it to do so.
The Constitution Court on Friday voted 6-3 to nullify the election because it was not completed on the same day as required by the charter.
Twenty-eight constituencies of 375 nationwide were unable to hold votes because no candidates had been able to register.
Pheu Thai also pointed out that Friday's court ruling created a problem. The Feb 2 polls could not run smoothly because anti-government protesters obstructed the peocess.
The judgement has now set a precedent, it said. If a new election is called, anyone could easily render it void by using the same tactics.
Pheu Thai also said the country's problems stemmed from the efforts by the People's Democratic Reform Committee (PDRC) to use unconstituional means to seize governing power.
For example, it wants an unelected people's council and prime minister. Yet when a petition was filed with the court against such an effort, the court rejected it, saying the protests were peaceful.
Pheu Thai also said the court's attitude, as well as how it came to power, was controversial. It was appointed by the Sept 19, 2006 coupmakers. Some of the judges drafted the 2007 charter they now defend, constituting a conflict of interest, the party added.
It concluded that the election was abused by "dishonest acts" of many stakeholders from the start — from the PDRC, the Democrat Party's boycott and the apparent reluctance of the Election Commission to proceed with it.
The remaining 50 parties, as well as 20 million people who turned out on Feb 2, now had to pay for abiding by the law while the court ruling rewarded the wrongdoers, it said.