Private aid companies and charities will be asked to reappear before MPs, after some of the evidence given on tackling sexual abuse was condemned as “completely unsatisfactory”.

Stephen Twigg, chair of the international development committee (IDC), said he intended to invite representatives of both groups back.

“We had some concerns with the evidence from Bond [the body that represents charities] but frankly, the concerns about the private sector are enormous – and nothing you have said today has served to reassure me,” said Twigg.

Rory Stewart, who appeared before MPs on Tuesday for the first time as secretary of state for international development, said dramatic improvements had been made on safeguarding over the past 12 months.

The IDC evidence session was held to take stock of the committee’s work into tackling sexual exploitation and abuse in the aid sector following the Oxfam scandal.

MPs were told that that last week’s meeting of a cross-sector network set up by private contractors to tackle sexual abuse was the first since the UK government’s safeguarding summit in October. MPs also heard that private sector companies had decided not to sign up to safeguarding commitments presented at the summit.

“The sector has decided that the commitments represent a suggestion for improvements, but that they felt it was more of a guidance,” said Tracey Smith, chief executive officer of British Expertise International, which represents 30 private sector suppliers delivering UK aid.

She told MPs that the commitments presented at the summit had been superseded by a code of conduct set by the Department for International Development (DfID), which was modified last year.

MPs also heard that there was no constituent within the sector monitoring reports of sexual misconduct among private contractors.

Smith said that BEI was not aware of the number of safeguarding incidents recorded by its own members, or if this had increased over the past year following efforts to encourage greater reporting.

“There are a number of conflicts there [preventing monitoring] in terms of information and [General Data Protection Regulation],” she said.

Smith was repeatedly asked by MPs to clarify what action private companies had taken to tackle abuse and harassment. “You’ve hardly met [up]. Nothing’s changed except something’s been inserted in the code of conduct,” said Pauline Latham, a member of the international development committee. “And then you’ve said: ‘DfID will monitor it.’”

Between January and August last year, 18 safeguarding incidents were reported by private contractors to DfID, according to a freedom of information request submitted by the Guardian. DfID did not have dates for all of the incidents on its records.

During the hearing Latham said “the NGO sector appear to have...been doing a better job than the private sector. I’m still not convinced that it’s good enough.”

Bond, which represents more than 400 UK aid charities, was also questioned by MPs over its work to improve reporting processes and whistleblower protection. DfID had told MPs that Bond’s working groups suggested that an audit of whistleblowing across the sector was unnecessary.

Frances Longley, chief executive officer of Amref Health Africa UK, and a representative of Bond working groups, said this was because the groups were instead focusing on other areas, including immediate action to improve reporting processes.

During the evidence session, Stewart confirmed his commitment to his new position, following his comments on Sunday that he would like to be prime minister. Stewart said he was entirely focused on his department, adding that he had spent “much more of my working life in international development than, I assume, anyone else who has taken over this job”.

• This article was amended on 13 May 2019 to make some of the references to the MPs’ criticisms more precise.