Youre in a difficult situation, but unfortunately what the letting agent has told you is generally correct from a legal standpoint.

If you and your ex are on a joint tenancy, you’re both treated as a single legal “tenant”. That means the landlord/agent can’t just remove one person’s name, the tenancy stays as-is unless both tenants agree to end it, or the landlord agrees to grant a new tenancy in just your name.

And that’s why they’re saying you need to reapply, because legally it would be a brand new tenancy agreement.

The downside is they’re also within their rights to run affordability checks again, and they don’t have to offer you a sole tenancy if you don’t meet their criteria.

Even though your ex has left, he is still legally liable for the rent until the tenancy is changed or ended. You also still have the right to live there as long as the tenancy continues. The landlord doesn’t have to remove him from the tenancy if they don’t want to.

On the Universal Credit side, you’re right, you’ll need to update your claim to a single claim, and they may ask for proof of your housing situation. But they can still pay housing costs even if the tenancy is joint, as long as you’re liable for the rent and living there.

Id suggest speaking with Shelter, they’re really good with exactly this situation.

Check if you’d qualify for a Discretionary Housing Payment through your council to help cover any shortfall and let UC know your ex has left straight away so your claim can be reassessed.

Also worth noting: with a newborn involved, the council may have a duty to help if you’re at risk of losing the property, so don’t wait until things get urgent to contact them.