Four residents of Grenfell Tower were accidentally left to die in an upper-floor flat after a mix-up during the rescue effort, an inquiry into the fire has heard.

Eight tenants from the 14th floor of the west London high-rise had been told by firefighters to hunker down in flat 113 and await rescue, but only four were taken out.

It emerged at the inquiry on Thursday that the team tasked with saving them were under the impression only a family of three were in the flat.

But, in adivergence of accounts, one of the rescue team, Peter Herrera, had his story called into question by Omar al-Haj Ali, a survivor whose brother died in the fire.

Herrera was accused of being mistakenand was challenged about how he could have missed four other people in the flat if he had looked properly.

The firefighter insisted he did not “make this up”. He finished his evidence, saying he was “very, very, very sorry” if anyone thought he had failed them.

Herrera told the hearing at Holborn Bars in central London that he had arrived at flat 113 to find the electricity out and the family of three, Oluwaseun Talabi, his partner and their young daughter. The family were reluctant to leave but he pulled them out and sent them down the stairs with his colleagues, he said.

He then noticed a silhouette in the flat, according to his written statement, which transpired to be Omar al-Haj Ali, whose brother Mohammad died later in the blaze.

The brothers had been with their 14th-floor neighbours Denis Murphy, Zainab Deen and her young son Jeremiah.

The firefighter asked the man if anyone else was left in the flat and was allegedly told: “No, I’m the last one.”

Haj Ali was rushed down the stairwell with Talabi and his family.

Herrera claimed he realised the mistake later in the night, when he saw Haj Ali outside the tower on the phone to his trapped brother.

The firefighter’s statement said: “He then went on to say: ‘I am still on the phone to him, he is on his knees praying.’ He also said: ‘I was mistaken.’ I remember saying to [the crew manager Benjamin McAlonen]: ‘Oh fuck’.

“There seemed to be some confusion as I recall ‘Syrian man’ being very clear earlier that no one else was in the flat. I said to him: ‘Don't worry, I will sort it out.’”

But Herrera’s version of both conversations was contested by Haj Ali, who was present at the hearing along with Talabi. Haj Ali said he never said the flat was empty, nor did he later say he had been “mistaken”.

The counsel to the inquiry, Andrew Kinnier QC, said: “Mr al-Haj Ali wants me to suggest to you that the account of that conversation is mistaken. Would your response be effectively the one you have already provided?"

“It must have been a mistake on one of our parts, yes,” Herrera replied.

Kinnier continued: “Mr al-Haj Ali would want to say that you didn’t come into the lounge. What would you say to that?”

The firefighter replied: “I was there and I know what I did. I spoke to the gentleman. He was there, I was there. I didn’t make this up. I was with him.”

The firefighter said he did not search the remaining rooms as he assumed there was no one there. Several of the remaining residents were found dead in flat 113, the inquiry was told.

Herrera was asked by Kinnier why he did not notice them, “if they were in there, if you looked properly”.

He replied: “That’s the thing, I didn’t see them, they weren’t there. Especially if I’m being told he was the last person, there was no need to look, from my point of view that flat was empty.”

Talabi could be seen shaking his head at the answer.

Earlier, the firefighter who made the initial decision to move the 14th-floor residents into one flat also apologised. Desmond Murphy assessed it was too dangerous to take the group down the smoke-logged stairwell and found flat 113 to have safe air.

He, colleague Charles Cornelius and two other firefighters, including Nicke Merrion, were forced to leave for the lower floors as they ran low on oxygen. They told their superiors at the operational hub that eight people, six adults and two children required rescue in flat 113, the inquiry was told.

Working hard to maintain composure, Murphy told Thursday’s hearing: “I would just like to say to the family members of Denis Murphy, and the family members of the other seven residents I came into contact with on the 14th floor, I’m very sorry we couldn't get your loved ones out of the building.”