The judge, Pablo Ruz, who issued the order late Thursday, said he took the step in part because of recent findings suggesting that Mr. Bárcenas held money in other countries, including the United States and Uruguay, in accounts that have not been frozen. Mr. Bárcenas, who is in a jail outside Madrid, is to be held without bail until a possible trial, for which no date has been set. His lawyers said they would appeal.
The denial of bail was one of the most dramatic developments to date in the case against Mr. Bárcenas, who is being investigated on suspicion of tax fraud and other financial crimes, including running a slush fund that made regular payments to Prime Minister Mariano Rajoy and other senior party officials.
After he resigned as treasurer in 2009, Mr. Bárcenas is believed to have left his office with nine boxes of documents. Asked on Friday whether he feared possible blackmail from his former treasurer, Mr. Rajoy said, “Neither now nor at any moment in the past has this occurred.” He called on the judiciary to handle the case “with celerity.”
The case against Mr. Bárcenas is a tangled one that continues to produce a steady trickle of revelations. He was originally subpoenaed four years ago in relation to what appeared to be a mundane graft case in which conservative mayors and other regional politicians from Mr. Rajoy’s party were accused of taking bribes from a group of businessmen led by Francisco Correa.
Mr. Bárcenas was initially cleared of wrongdoing, but last January the Swiss authorities revealed that he had amassed 22 million euros, or $28.6 million, in secret bank accounts. Since then, the total has risen to at least $61 million, officials say, and prosecutors are investigating whether Mr. Bárcenas has undeclared funds elsewhere.
In recent weeks, investigators have produced further evidence against Mr. Bárcenas and other members of the Popular Party relating to their ties to the business network led by Mr. Correa. Among the most recent was that Mr. Correa paid for part of the wedding in 2002 of the daughter of José María Aznar, who was the conservative prime minister at the time. The Aznar family acknowledged receiving a wedding gift, but has denied that Mr. Correa received any special favor in return.
Mr. Bárcenas has offered a variety of explanations for his wealth, including that he held money on behalf of other investors. He has also claimed profits from successful stock and real estate transactions, as well as the sale of restored paintings.
Several recent witnesses, however, have cast doubt on his explanations. This past week, Isabel Mackinlay, a painter whom Mr. Bárcenas claimed to have hired to sell paintings in Buenos Aires, told the judge by videoconference that she had never met Mr. Bárcenas, but had received a payment to facilitate some fictitious painting transactions.
As part of the slush fund investigation, some of Spain’s most powerful construction entrepreneurs have been subpoenaed by Judge Ruz, but have denied any wrongdoing and instead acknowledged making some declared donations to political foundations.
The fiscal crimes unit of the Spanish police released a report last month in which it said it had identified 19 of the fund’s corporate donors, which received more than $15 billion worth of public contracts from conservative politicians over a decade.