Ministers have ordered yet another review into why some flood-hit homes cannot get insurance and promised another £1m to help those affected after around 100 homes were hit over Christmas.

Theresa Villiers, the environment secretary, said she was commissioning an inquiry into why some flooded communities were unable to get sufficient insurance, despite an agreement between insurers and the government in 2015 that was supposed to mean everyone would have access to affordable cover.

Boris Johnson has been criticised for failing to visit any of the areas affected in the latest round of flooding. The prime minister spent Christmas in Downing Street with his partner, Carrie Symonds, and the pair are expected to fly to the exclusive private Caribbean island of Mustique to see in the new year.

Areas of southern England and north Lincolnshire are still at risk of groundwater flooding, with 88 warnings still in place and 100 properties having flooded since last Thursday.

Before that, 4,200 homes in South Yorkshire and surrounding counties were flooded during the election campaign in November.

Ministers said on Thursday that a charity that helps flood victims in South Yorkshire would get another £1m of funding, while other areas have been given £300,000.

Robert Jenrick, the communities secretary, said the flooding had been “devastating” but he praised the role of charities and volunteers in helping families whose homes have been ruined.

“But more support is still needed, which is why we’re matching money raised by the South Yorkshire Flood Disaster Relief Appeal Fund pound-for-pound, to help vulnerable people facing hardship to recover and get back on their feet,” he said.

There was a major review of flood insurance in 2008 and the government spent years in talks with insurers before reaching the Flood Re agreement in 2015.

But Villiers appeared to acknowledge there were problems with the system as she ordered another review.

“We have listened to communities that have been affected by flooding and understand just how important it is to ensure that everyone is able to access sufficient insurance cover,” she said.

“That’s why we will be reviewing insurance cover following the recent flooding to understand any lessons to be learned for the future.”

Earlier this month, Dan Jarvis, the mayor of Sheffield city region, said there were problems with Flood Re, the government-backed scheme that promised to provide insurance for domestic properties deemed at significant risk of flooding. “I don’t think this scheme has worked,” he said, suggesting that central government had a “moral duty” to help those unable to get insurance.

The government said 20 million households now have buildings insurance that covers flood risk and the introduction of Flood Re has seen four out of five households with a previous flood claim getting price reductions of more than 50% for their insurance.

However, the recent flooding has seen reports of people not having sufficient insurance cover, which has triggered the latest review.

As well as reviewing insurance, Johnson has also faced calls to overhaul the system for deciding where flood-defence funding is spent and launch an emergency response unit to prevent a repeat of the catastrophic damage caused by the November floods.

The Environment Agency warned on Thursday that communities needed to remain vigilant.

Clare Dinnis, a flood duty manager at the agency, said: “While the weather outlook is improving, groundwater levels continue to rise after recent rainfall meaning that there is a continued risk of groundwater flooding in parts of southern England over the next few days.

“We continue to monitor rainfall and river levels closely and to operate our flood defences, reducing the risk of flooding to thousands of homes and businesses and helping to keep people safe. Our pumps also remain in place in Somerset where our focus is on reducing levels of water on Currymoor.

“Sadly around 100 properties have flooded since Thursday, but over 18,500 properties have been protected by flood defences across England.

“We advise people to sign up for flood warnings, stay away from swollen rivers and not drive through floodwater – just 30cm of flowing water is enough to float your car.”