An MP has spoken of her disappointment that as few as three MPs were present at an inquiry into making sex education compulsory in schools.

The education select committee heard from eight professionals in its first session on personal, social, health and economic education (PSHE), and sex and relationship education (SRE).

For most of the two-hour hearing, only three MPs remained in the room – the least a committee can have and still be quorate.

A bill put forward by Green MP Caroline Lucas for statutory PSHE, and for SRE to be a mandated as part of those lessons, will today have its second reading in Parliament.

Ms Lucas said she was “disappointed” most members were unavailable to attend the Tuesday meeting.

Chairman Graham Stuart and Siobhain McDonagh stayed for the whole meeting, while Neil Carmichael attended the first session – in which four witnesses gave evidence – with Pat Glass arriving for the second. During the meeting, Mr Stuart told witnesses: “I should probably point out as we are being broadcast, and my colleague [Pat Glass] has just arrived from sitting on one bill committee, that colleagues are sitting on various bill committees right across the House since early today. That, and that alone, is the reason why they are not sitting on the committee today.”

He said he wanted to clear up any misapprehension that “MPs are lying in their beds instead of working long and hard which is what they generally do.”

A day later seven MPs were present when Nicky Morgan gave evidence on academies and free schools.

An education committee spokesperson said: “In a given week for a main meeting, Wednesday would be the preferred day.

“Members will have to juggle and the meeting [on a Tuesday] is considered to be less of a priority for them. If they are on another committee, it is just a practical issue. If that committee only meets on that day and the education select committee meets twice, then they will make that decision.”

Ms Lucas said: “It’s disappointing that so few attended the meeting to hear the evidence. I’ve been hugely encouraged by the widespread support on this issue, including on my own Private Members’ Bill that aims to make PSHE a statutory requirement.

“It’s such an important debate to be having and I’m very pleased that it’s now happening across all parties. MPs can be incredibly busy, but it’s crucial they’re well informed on such important topics being discussed in Parliament.”

During the meeting there was overwhelming support from witnesses for PSHE to be statutory.