A surveillance officer listening in on a man accused of plotting to kill Celtic manager Neil Lennon told a court her identification of the speakers may have been "inaccurate".

The officer, who police have requested is not identified, was involved in listening to material recorded by a secret bugging device in Neil McKenzie's car.

Last May it picked up a conversation mentioning a bomb. In the tape, which was played to the jury at the High Court in Glasgow, a male voice was heard to say: "I told thingummy how to build a bomb."

On Tuesday, the officer told the court she had identified the speaker as McKenzie.

But under cross-examination yesterday from Donald Findlay, QC, for McKenzie, she said there were two speakers.

Mr Findlay put it to the officer: "One person did not say all of those words, so you are wrong. It's absolutely clear that more than one person is speaking."

The officer replied: "I didn't believe so."

Mr Findlay then said there were "quite absolutely two different voices".

She replied: "It sounds like it."

The lawyer said: "So you were wrong?"

She said: "It is inaccurate, yes."

Mr Findlay suggested the recording "may not have been said by the subject at all".

She replied: "In my opinion, it was the subject I heard."

McKenzie, 42, is accused along with Trevor Muirhead, 43, of conspiring to murder Mr Lennon, ex-MSP Trish Godman and the late Paul McBride, QC, in an explosives plot, as well as various people in the premises of Irish Republican organisation Cairde Na Heireann.

It is alleged they sent improvised explosive devices to them between March 1 and April 15 last year, and it is also alleged they believed the devices were capable of exploding.

The pair face an alternative charge of conspiring to cause an explosion of a nature "likely to endanger life or cause serious injury to property".

They deny all the charges.

The trial, before Lord Turnbull, continues.