* Medvedev gives interview, backs Putin on new laws
* Media speculate ex-president will be dismissed
* Medvedev's standing has fallen, mocked on Twitter
MOSCOW, Dec 7 (Reuters) - Russian Prime Minister Dmitry Medvedev on Friday defended new laws which opponents say will be used to stifle dissent, underlining his allegiance to President Vladimir Putin after talk of a rift.
In a live interview with five Russian television stations, Medvedev appeared determined to show he is in step with Putin and to silence rumours that the more hawkish president could sack him as premier.
Asked about new legislation which forces lobby groups funded from abroad to register as "foreign agents", Medvedev dismissed concerns that the term was deliberately pejorative because it evokes the Cold war.
"What's wrong with the word 'agent'?" Medvedev said. "Agent means 'representative', and that's all ... Anything else is just a coincidence."
He also dismissed suggestions that the passage of laws in the last six months broadening the definition of treason, raising fines for protesters and increasing fines for defamation was part of a trend signalling a clampdown on the opposition.
"I do not take it as a trend. I do not agree these laws are reactionary," he said.
Medvedev, 47, stayed on message throughout the 90-minute interview, broadcast across the nation five days before Putin delivers his annual state of the nation address.
His remarks revealed none of the differences that have occasionally emerged between Putin and Medvedev, notably over the Libya conflict in 2011 and, to an extent, over the trial of the Pussy Riot punk band for its anti-Putin protest this year.
Putin and Medvedev worked together in St.Petersburg in the 1990s, and it was the former KGB spy who ushered his more liberal protege into the presidency in 2008 because the constitution bars three successive terms.
But there has been talk of a rift since Putin rebuked the government in September over its fiscal plans and the conduct of cabinet ministers, and Medvedev criticised the president's methods of dealing with business leaders.
FALL IN STANDING
Medvedev's standing has declined sharply since he and Putin announced in September last year that Putin planned to return to the presidency, ending speculation that Medvedev would stay on.
A think tank, the Institute of Globalisation Problems, said in a report this week that Medvedev was likely to survive as premier only until March or April because of battles behind the scenes between rival interest groups.
Other political experts say Putin is more likely to keep Medvedev in place at least until there is an economic slowdown or another crisis that requires a high-profile scapegoat.
Medvedev ignored the rumours in Friday's interview, during which he was asked about drunk driving and a possible ban on smoking in public places, and denied the world would end on Dec. 21 under a New Age prophecy.
He said he might have another tilt at the presidency one day if the Russian people want it. But the reaction on social media was discouraging, especially after footage appeared on YouTube of the journalists asking him after the interview if he believed in Father Frost (Father Christmas) and what presents he wanted.
"It's sad when the former president and current prime minister of your country is simply a pathetic person," wrote Yekaterina Kudinova on Twitter.
Another, identified as Borman, wrote: "Journalists, stop mocking the baby ... It's time to sleep."