Britain is going into closer relations with China with its "eyes wide open", the Foreign Secretary has insisted as the state visit by President Xi Jinping gets under way.

Ministers expect more than £30 billion of trade and investment deals to be struck during the four-day visit that will see the UK pull out all the stops to court the leader of the world's second-largest economy.

Critics have warned that Britain will "rue the day" it forged deeper ties with China and accused the Government of acting like a "panting puppy" in its relations with the country.

But Philip Hammond insisted the move was in the national interest.

He told the BBC: "I don't think we are naive. It's very much in our national interest to engage with China but we do so with our eyes wide open."

Mr Hammond said the United States remained Britain's closest ally but that did not stop the UK from working with China.

"I think we are developing a mature relationship with the Chinese," he said.

"They know that we are looking not just to China but to many other countries for infrastructure investment in the UK." 

Prime Minister David Cameron has hailed the visit as an "important moment" in relations between the UK and Beijing but is facing pressure to raise concerns over human rights and the "dumping" of cheap steel with the Chinese leader.

Mr Hammond said "substantial tariffs" had been imposed on Chinese steel imports but insisted "we can't simply build a wall around the UK".

"If we had steel prices in the UK that were far out of line with the steel prices in other countries, our downstream industries would not be able to be competitive with the products they produce," he told Today.

"So, we have got to get the balance right. Trying to protect our steel industry in a sensible way, which we are doing, but recognising that we operating in a global economy and we can't simply build a wall around the UK."

Downing Street has rejected accusations of "kowtowing" to Beijing for the sake of commercial deals, insisting that no subject will be off the table in talks during the state visit.

But China expert James McGregor warned Britain would now be seen as being "on a leash" by the Chinese leadership.

The chairman of consultancy group APCO Worldwide's Chinese operations said: "This is incredible what's going on right now, with the British Government saying 'we want to be your best friend, we want to be your best friend, we'll do anything for it'.

"Well, if you act like a panting puppy, the object of your attention is going to think they have got you on a leash.

"China does not respect people that suck up to him. England is going to rue the day they did this," he added.