A lower proportion of calls is being answered by HM Revenue and Customs (HMRC) than would have been the case if a helpline shake-up had gone through, MPs have heard.

Jim Harra, chief executive of HMRC, told the Treasury Committee that if the revenue body had been able to proceed with the plans, more vulnerable and digitally excluded customers would have been helped.

HMRC announced plans to shake up its helpline services on March 19, which would have seen the self-assessment helpline closed for some of the year.

But on March 20, following an outcry from a range of bodies – including tax and accountancy professionals and small businesses, it halted the plans.

The plans would have meant that, between April and September, the self-assessment helpline would be closed and customers would be directed to self-serve through its online services.

Mr Harra said the decision not to proceed with the changes was made following a “strength of feeling” from stakeholders which had not been expected.

He told the committee: “Ministers certainly expressed their concern about the strength of the reaction and about the fact that the reaction was not just a, it wasn’t just a political reaction, it was actually a genuine concern about how’s this all going to work.

“And we quickly agreed that the right thing to do was not to proceed with this and to listen to these concerns and to make sure that we have either addressed them or if we haven’t that we take them on board and re-plan and so that’s why we decided not to proceed.”

He said HMRC is continuing to invest heavily in digital services and to encourage customers to use them as their first port of call if they possibly can, but helplines will remain open in the usual way.

Asked about the effects of not implementing the changes announced on March 19, Mr Harra said: “The key pressure point is in our helpline service, where we are giving a service to customers well below the service standard that we want to give them, whether that be wait times or whether that be the proportion of calls that succeed in getting answered by an adviser.

“And today, a lower proportion of those calls is being answered than would have been the case if we’d been able to implement these changes.

“Because customers who we would have deflected to the online services are today going through to those helplines.”

He said HMRC had to re-plan to get service levels back up as high as it can.

Mr Harra said he had had “positive and constructive” discussions with ministers.

Asked if he was worried that things would get worse, Mr Harra said: “Certainly in the short term I think that we are in for a very difficult first quarter. I would hope that going into the second quarter that we will be able to make improvements with additional resources as well as continuing to push our digital first strategy at every opportunity.”

He added: “I think there’s little doubt that if we had been able to proceed, the evidence from last year’s trials indicates that we would have been able to help more vulnerable and digitally excluded customers because the route through to an adviser for them would not have been blocked by other callers whose calls could have been more effectively dealt with online.”

Mr Harra said there are “lessons for the department in how we engage with stakeholders”.

Speaking earlier about the announcement made on March 19, Mr Harra said: “HMRC decided that we thought it was a good idea to do this based on the results of the trial last year, but that was shared with ministers.”

Asked if they knew the date, he said: “Yes.”

Asked who the stakeholders were who caused the decision to be reversed on March 20, he said: “We got an immediate reaction from a range of stakeholders, including tax professional bodies, that expressed concern that despite the trials last year and despite the evaluations of those, that we were moving too fast.

“And that they did not have the assurance they needed that we would be able to provide services for example to those customers who could not do things online.

“And we concluded that the best thing to do would be to stop the changes that we had announced.”

Asked if he had not run this by his external stakeholders before March 19, Mr Harra said: “Yes we had spoken to stakeholders, in particular tax professional groups, we knew that they preferred us not to proceed with it. Frankly, they would prefer us not to make these significant changes at all but to be resourced in the way that we’ve always done them.”

He added: “I’m not saying there were new stakeholders who came out of the woodwork… what there was was a strength of feeling from stakeholders, which was not what we had been expecting and which expressed concerns about matters that I believe we will be able to demonstrate to stakeholders we have taken account of.”

He said HMRC’s strategy “is still a digital first strategy…

“What we have said that we will do is we will engage with stakeholders further on how we can safely implement out digital first strategy, and that may mean doing it more slowly than we had originally planned.”

Put to him that this would not make the concerned stakeholders feel very different, he said: “A lesson for us is that we did an extensive evaluation of the two trials, but we only published that on March 19 so people externally had not had the opportunity to absorb that in the same way as we had and Ministers had.

“So I think we need to go through all of the concerns that stakeholders have, all of the evidence for whether those concerns are justified or not and our plans for how we will address them.

“In the meantime, we will undoubtedly be implementing our strategy more slowly than we said we would on March 19.”