Updated 6.00pm - adding that Dr Cardona is to sue.
Economy Minister Chris Cardona was "hedging his reply" when denying claims that he visited a brothel while on an official government visit to Germany, Nationalist shadow minister Beppe Fenech Adami said.
"I expect Chris Cardona to come clean and say whether he visited a brothel during any time on his trip to Germany," Dr Fenech Adami said.
Dr Cardona this morning said he "categorically denies allegations...on his whereabouts during an official government visit in Germany" and called them "a prime example of fake news".
The allegation was made by blogger Daphne Caruana Galizia, who in a post uploaded late last night said that Dr Cardona had been spotted at the FKK Acapulco club just outside Duesseldorf. She has stood by her claims.
The FKK Acapulco advertises itself as a "sauna club", with services including stripteases, gogo girls and "30 fully air-conditioned top suites".
Ms Caruana Galizia claimed that the minister had been spotted at the club in the company of an unidentified "short and bald" man.
Dr Cardona is currently in Germany take part in a forum on the digitisation of European industry.
"This outright lie is another attempt on Caruana Galizia’s part to discredit and sully an individual’s reputation," Dr Cardona said in an official statement issued by his ministry.
The minister said that he would continue to work to attract investment and create job opportunities. He did not say whether he would be taking any further steps.
In a subsequent blog post, Mrs Caruana Galizia stood by her claims and said Dr Cardona was lying.
Dr Cardona responded by saying he would sue. "In light of Daphne Caruana Galizia’s perseverance in the spreading of lies and fictitious reports on Minister Cardona, despite the categorical denial that was published earlier today, the minister has no choice but to institute legal proceedings against the blogger," his ministry said.
Last month, Dr Cardona's ministry was flagged by the Auditor General after the NAO discovered that the minister and two of his aides had charged a €758 minibar bill, including €438 spent on alcohol, to the public purse following a trip to Dubai.
A ministry spokesperson had later said that the money would be refunded, adding that alcohol "is known for being quite expensive in Dubai”.