FORMBY High School was closed to around 700 pupils on Thursday, October 8 due to blocked drains in the Freshfield Road area.
Sefton Central MP Bill Esterson said: “My office received a call from Formby High School asking for help to contact United Utilities about blocked drains and backed up sewers in the Freshfield Road area.
"The school had had their own drains response service out as they thought it was a problem on site, but they discovered it was an issue with the main drains on Freshfield Road.
"United Utilities had promised the headteacher they would be out to investigate on Wednesday by 10pm, but later admitted that they would not be sending a team. This left the headteacher in a very difficult position to announce a partial closure of the school just hours before the children were due back in on Thursday morning.
"My office was able to contact United Utilities on Thursday and they were on site by Thursday lunchtime discussing the situation with the headteacher.
"United Utilities should have attended when they said they would. Around 700 children missed school today, at a time when children need to be in school more than ever to catch up on work missed and with the ongoing potential threat of Covid closures and quarantine.
"United Utilities tell me the issue is that the local sewer network was full after the recent prolonged heavy rainfall. I will be asking for a further update regarding what actions will be taken to avoid a repeat of this in the future."