The official Tass news agency on Wednesday called the founders of a new Soviet political party liars and scandalmongers whose actions hamper Soviet leader Mikhail S. Gorbachev's reform drive. It the first attack by the state-run media on the new Democratic Union, Tass accused members of ``slanderous, anti-social activity.'' The toughly worded dispatch indicated that officials would not tolerate any challenge the new party might mount to the ruling Communists. Past attempts to challenge the Communist Party have been crushed. About 70 people met Monday outside Moscow to create the new party, which seeks multi-party elections, independent trade unions, a new constitution and the withdrawal of Soviet troops from Eastern Europe and areas seized by the Soviet Union in World War II. Members of the Democratic Union expressed the hope that if Gorbachev is serious in his campaign for a more open society, he will allow the party to seek supporters and take part in elections, which are tightly controlled by the Communist Party. Tass said the Democratic Union's platform was a ``provocation with a political flavor'' that was so anti-constitutional it touched off arguments among group members and exposed its authors to criticism from the group itself. ``The group is nothing more than a bunch of scandalmongers deliberately smearing honest people and hampering perestroika and efforts to foster good relations between people,'' the Soviet news agency said. ``Perestroika,'' which means ``reconstruction'' in Russian, is the name given to Gorbachev's ambitious reform program for economic and social restructuring. Tass did not say why the Democratic Union's ``Declaration of Principles'' was unconstitutional, but the 1977 Soviet Constitution enshrines the Communist Party's monopoly on power, calling it the ``leading and guiding force'' of the country. Tass also defended the jailing of Sergei Grigoryants, the founder of the independent human rights journal ``Glasnost,'' who was arrested Monday. Grigoryants, a former political prisoner, had offered to let the Democratic Union group use a country cottage outside Moscow that he rents for their Monday meeting. But police surrounded the building, arrested Grigoryants in the yard, and broke down the cottage's doors to arrest others, associates of Grigoryants told a Moscow news conference Tuesday. The Tass account of Grigoryants' arrest said: ``On May 9 ... he kicked up a violent row on a trip outside Moscow and has been sentenced to seven days in jail by the People's Court of Ramenskoye in the Moscow region.'' Grigoryants, a former political prisoner, was convicted on a charge of resisting authorities. Andrei Babitsky, a fellow editor of ``Glasnost'' who was also detained at the cottage but later released, said Grigoryants had been falsely accused. Lawyer Valentin Yelisyenko, who also spoke at the dissidents' Tuesday news conference, said police had no arrest warrant for Grigoryants or any of the others arrested and had search warrant to enter the cottage.