Democrat MP Boonyod Sooktinthai will ask the National Anti-Corruption Commission to investigate budget spending by House Speaker Somsak Kiatsuranont.
Mr Boonyod, a spokesman for a committee on House affairs, said the panel has looked into the spending by the House Speaker and a group of MPs for their trip to the UK between Sept 20-28.
The panel summoned Sompol Wanikphan, deputy secretary-general of the House of Representatives, to explain the matter.
Mr Sompol told the panel the money spent on the trip was drawn from a budget for democracy development.
However, the democracy development budget can only used for domestic trips so a specific budget for overseas trips must also be allocated.
Mr Boonyod said about 1.06 million baht was paid for air tickets for the group comprising Mr Somsak and nine MPs.
Mr Boonyod said Mr Somsak alone spent about 2.89 million baht on the nine-day trip. The expenses included 15,500-baht allowances and room charges totalling 120,000 baht. Mr Boonyod said Mr Somsak's transport costs were up to 2.24 million baht.
He suspected the budget could have been misspent.
Mr Boonyod said he will forward the matter to the NACC and if there are grounds to the case, Mr Somsak could be removed from his position.