* Lawmaker accuses Interbolsa of money laundering
* Another 11 brokerages under investigation, lawmaker says
* Minister calls for tighter regulations in capital market
BOGOTA, May 9 (Reuters) - Colombian Finance Minister Mauricio Cardenas on Thursday described the collapsed Interbolsa brokerage as a "launderette" and a "sewer" after accusations from a lower house lawmaker that it laundered cash from drug cartels and Marxist FARC rebels.
Interbolsa, the largest brokerage in the fast-growing Andean country, was intervened and dissolved in November following a liquidity problem that left it unable to make $11 million in scheduled bank payments.
A criminal investigation by the Attorney General's office is under way to establish whether there were possible conflicts of interest, share price manipulation and "hiding" of information by the brokerage.
But lawmaker Simon Gaviria on Wednesday went a step further, accusing Interbolsa of laundering money from drug cartels, crime gangs and the Revolutionary Armed Forces of Colombia, or FARC, the Marxist group that has been waging war against the state for five decades.
Gaviria, head of the Liberal Party and son of former President Cesar Gaviria, said another 11 brokerages are being investigated by United States authorities for money laundering.
Gaviria declined to name his sources, saying that he did not want to harm the ongoing investigations.
"There is money with links to the FARC, (Mexican drug boss) Chapo Guzman, the (criminal group) Oficina de Envigado, among others. The investigations are ongoing, and we could see some arrests that may lead to extraditions in relation to these activities," Gaviria said.
Interbolsa could have been used to launder money coming from bribes paid in exchange for public contracts, Gaviria said, claiming Interbolsa used subsidiaries outside Colombia as well as ghost companies for the illicit operations.
Finance Minister Mauricio Cardenas, who attended the hearing in Congress alongside Central Bank head Jose Dario Uribe, said he was aware that Interbolsa had been accused of manipulating share prices and channeling money to tax havens.
"But what we heard yesterday was another thing, it suggested (Interbolsa) was a launderette to, among other groups, cartels that won contracts," Cardenas told local radio.
"The attorney's office will have to clarify that ... but what strikes me the most is that every time you dig into this Interbolsa thing, you find more and more irregularities."
No one at Interbolsa's headquarters in Bogota was available for comment on Thursday afternoon. Reuters also tried to contact a company lawyer, but he could not be reached.
The Inspector General's Office is also gathering evidence to see whether government bodies or ministries failed to properly monitor the brokerage.
Cardenas said that most of the 1.8 trillion pesos ($983 million) worth of assets that Interbolsa managed had already been returned to the brokerage's clients. He said that regulations in the stock market will be tightened to prevent irregularities.
Rupert Stebbings, analyst at Valores Bancolombia in Medellin, said the accusations were a bit extreme, but that they should be understood as a warning sign for the market.
"This whole sorry episode needs to serve as a watershed moment for a market, which in truth has much stricter regulation than most others in Latin America, to fine tune procedures and clamp down on various areas."
Colombian regulators in November ordered the reorganization of Interbolsa SA, the brokerage's parent company, in a bid to restore confidence in the country's capital markets.
The brokerage had about 50,000 clients and accounted for about one-third of daily operations on the stock market. (Additional reporting by Carlos Vargas; Writing by Eduardo Garcia; Editing by Helen Murphy and Andrea Ricci)