Russian President Vladimir Putin says officials are still considering how to respond to the alleged UK spy scandal, but doubts expulsion will be necessary.
The TV report showed what it said was a UK diplomatic spy
He said he was still waiting for reports from the FSB security service and the foreign ministry.
"If these spies are sent out, others will be sent in. Maybe they'll send some clever ones that will be hard for us to find later," he told the media.
The furore followed footage of alleged agents getting data from a fake rock.
Mr Putin said he did not want "to exacerbate the situation and (had) no intention of souring our relations with our partners", according to Itar-Tass.
The UK Foreign Office expressed surprise and denied any improper behaviour when the allegations were first aired in a Russian TV report.
The programme said four officials from the UK embassy and one Russian citizen, allegedly recruited by the British secret service, downloaded classified data from a transmitter in a fake rock planted in the street onto palm-top computers.
The programme also said a UK diplomat made regular payments to Russian non-governmental organisations.
Mr Putin, a former KGB agent, added: "It is regrettable that there are attempts to work with NGOs using special services as the instrument to do so."
On Wednesday, the lower house of the Russian parliament, the Duma, passed a resolution condemning what it said was the funding of Russian human rights and civic groups by foreign intelligence agencies.
The Duma said such behaviour was unacceptable, and undermined trust in civil society. The Russian authorities have repeatedly alleged that Western governments and foreign spies have been pouring money into Russian non-governmental organisations with the aim of fomenting political unrest.
Earlier this month, Mr Putin signed a law giving authorities increased powers to monitor the activities and finances of NGOs.