Vyacheslav Volodin, a senior member of Medvedev's United Russia party, defended the move, saying Medvedev was already meeting ordinary citizens in extensive travel across Russia and that television debates would disrupt his schedule.
Volodin said: "The most important thing for us is real deeds, meeting people and solving actual problems, not wrangling in a TV studio."
Zyuganov, 63, who lost to Boris Yeltsin, the late president, in 1996 and was soundly beaten by Putin in 2000, said: "I now see they (the Kremlin) have frightened Medvedev. They are afraid to face us in a tete-a-tete dialogue."
Apart from Zyuganov, Medvedev will compete with Vladimir Zhirinovsky, a pro-Kremlin nationalist, and Andrei Bogdanov, a little-known independent.
Russia's election commission has already disqualifed Mikhail Kasyanov, an ex-prime minister, from running.
"The authorities are afraid of any discussion, any risk," Kasyanov told Ekho Moskvy radio and repeated his call for opposition candidates to boycott the poll.
"My insistent recommendation is that you do not take part in this farce, this special operation," he said.
However, Zyuganov has reiterated he will not quit the presidential race, saying if he did voters would have no genuine choice.
The argument came as Medvedev unveiled his pre-election programme in Moscow on Tuesday.
He said he wanted to double pensions and increase wages if he won power.
"We need to support the elderly and raise the average pension above the subsistence level. We plan to double pensions already in the next few years," Medvedev said during a meeting with trade unions.
Pensioners, who make up about one-fifth of the country's population of 140 million, have traditionally voted for communists but appeared to have shifted their sympathies in favour of pro-Kremlin parties in the last parliamentary election.
Medvedev said he wanted the government and employers to work together to boost "the pension capital" but did not elaborate.