As a survey revealed that a quarter of gay men see their sexuality as a barrier to becoming parents, Sir Tony Hawkhead, chief executive of Action for Children, said:
In the UK there are 6,000 children waiting to be adopted and we know that gay men can make loving fathers.
If more people came forward we would be able to help give loving homes to thousands of children.
We need to make sure that everyone knows that they can adopt - so by next year many more will celebrate their first Father's Day.
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The suspect, 35-year-old Willie Corey Godbolt, has been arrested and was being treated for a gunshot wound in hospital.
Mohanna Abdhou, known as Montana, was out with friends when two attackers cycled up to them and opened fire in Brent, north-west London.
The US president tweeted that Mrs May gave him "full details" of the incident during talks while he attended summits in Europe.