The U.K. has been wooing China in an effort to persuade the state and private investors to finance an array of expensive projects in the U.K.

But, as Chinese President Xi Jinping arrives Monday for his first state visit to the U.K., London’s courtship of Beijing is drawing criticism at home and unsettling allies, including the U.S., where officials have expressed apprehension about the U.K.’s approach.

Mr. Xi and his wife, Peng Liyuan, are due to stay at Buckingham Palace, where they will have lunch with Queen Elizabeth II on Tuesday. Later in the day, Mr. Xi will deliver an address to lawmakers at Westminster, where the U.K. Parliament sits. The weeklong visit will also include a meeting with Prime Minister David Cameron and a trip to the northern city of Manchester, where China has invested in infrastructure.

China sees President Xi’s visit as a chance to build on his efforts during a U.S. trip last month to showcase the commercial opportunities presented by China’s rise, while playing down concerns over its military power, human-rights record and economic outlook.

The U.K. government’s current China policy marks a contrast to the more-skeptical approach of the U.S.

As Washington and Beijing appear to be increasingly polarized, the U.K.’s eagerness to build ties provides an opportunity for China to build relations with another Western power, said Michel Hockx, director of the China Institute at SOAS University of London.

It also contrasts with the U.K.’s own relations with China just a few years ago, which turned chilly after Prime Minister David Cameron met with the Dalai Lama, the exiled Tibetan spiritual leader, in 2012, a nod to U.K. concerns about cultural and religious freedom in Tibet. China, which views the Dalai Lama as a separatist, responded by suspending some diplomatic meetings.

But the U.K., eager to foster ties with the world’s second-biggest economy, has sought to position itself as Beijing’s “best partner in the West,” and Treasury chief George Osborne said the U.K. wants to “create a golden decade” for the two countries.

Despite concerns about slowdown in China’s growth, the U.K. sees a big opportunity in boosting its relatively small exports and is eager to attract much-needed investment from overseas in British infrastructure and other projects.

In March, the U.K. became the first major Western nation to apply to join a China-led Asian Infrastructure Investment Bank, despite U.S. efforts to lobby allies not to join. The move raised concerns among U.S. officials because the new institution challenges Washington’s influence through the World Bank. Mr. Cameron said in an interview with China Central Television on Friday that the U.K. doesn’t see its involvement in the China-led bank as conflicting with its special relationship with the U.S.

The U.K. last month paved the way for China’s first nuclear project in the West, saying it would underwrite £2 billion ($3.09 billion) in Chinese financing for a new nuclear power station in England’s southeast to encourage Chinese investment. The U.K. government has given French nuclear giant Electricite de France SA and its partners, China General Nuclear Corp. and China National Nuclear Corp., a license to build two new nuclear reactors at Hinkley Point in southwest England. But the £24.5 billion project, the first new nuclear plant in a generation in England, has been held up by regulatory delays and talks with Chinese partners to finalize the terms on the financing. EDF has yet to make a final investment decision for the project to proceed. The company had initially said it expected to make the decision by late 2012.

Britain has been far less outspoken than the U.S. on contentious issues such as alleged Chinese cyberattacks—though British firms have also been targets—and on China’s island-building in the South China Sea. In the U.K., some lawmakers and commentators have voiced security concerns about Chinese ownership of critical assets. In 2013, Parliament’s security watchdog, the Intelligence and Security Committee, said Britain had potentially left itself vulnerable to cyberattacks and state-sponsored spying by allowing Chinese telecommunications giant Huawei Technologies Co. to become a major player in the country’s telecommunications industry. Huawei denies any links to the Chinese government or military.

The British government has also faced criticism from opposition politicians and human-rights groups who say it hasn’t been vocal enough on China’s rights record, an issue that critics are expected to raise during Mr. Xi’s visit.

Last month, Mr. Osborne became one of the first senior Western officials to visit China’s northwestern region of Xinjiang, where separatist unrest among the ethnic Uighur population has been simmering for decades. Rights groups accuse China of widespread abuses and systematic discrimination against Uighurs.

The government says that it has concerns about a range of civil and political rights issues in China and that it has been candid with the Chinese on areas on which the two don’t see eye to eye.

Chinese officials have defended China’s human-rights record, saying it has made significant progress in this area and that criminals are tried through a just, legal process.

The U.K.’s approach appears to be paying some dividends. Chinese investment into the U.K. has grown significantly in recent years, taking stakes in many corners of U.K. business and infrastructure—from London’s water supply to Heathrow Airport to cereal maker Weetabix Ltd.

Since 2012, total Chinese investments and construction contracts in Britain have amounted to about $20 billion, more than doubling the inflows of the preceding seven years, according to data compiled by U.S.-based think tanks Heritage Foundation and American Enterprise Institute.