AIDES close to patriarch Mr Deng Xiaoping have moved to shore up his authority in the wake of challenges by conservative elders including Mr Chen Yun. For the first time since Mr Deng came to power in late 1978, central organs including the Propaganda Department have officially designated Deng Thought as the party and state ideology. Analysts said this was in response to a series of messages that Mr Chen had sent senior cadres on his alternative approach to running the country and economy. According to the People's Daily, the Propaganda Department has issued a circular to all party and government officials to include Deng Thought in their regular ideological study sessions. The Central Committee Archives Research Office has recently published a primer called Selections of Comrade Deng Xiaoping's Theories of Building Socialism with Chinese Characteristics, which is now required reading for cadres as well as students. The circular said Deng Thought was a ''synthesis of the basic theories of Marxism and the reality and present-day characteristics of contemporary China''. ''They are a continuation and development of Mao Zedong Thought and they represent modern Chinese Marxism.'' Mr Deng's theory of radical economic reform coupled with tight political control was enshrined as the party's guiding light at the 14th party congress last October. However, Mr Deng himself is reported to have resisted the establishment of a ''personality cult''. Chinese sources said the escalation of the campaign was partly due to the patriarch's declining health. This is despite new reports yesterday that Mr Deng was in excellent health and that he was fit enough to travel. A report in the Beijing-funded Wen Wei Po of Hongkong said the patriarch had on Wednesday taken the night train from Shanghai back to the capital. The sources added, however, that the major reason for the propaganda campaign was to deflect the challenge from Mr Chen and other conservative elders. A report in yesterday's Hongkong Economic Journal said Mr Chen had written a letter to the Central Committee late last month explaining his views on economics, politics and personnel. Mr Chen, 88, reportedly warned against ''overambitiousness'' in economic policy, saying that areas including the stock market and real estate had become dangerously overheated. Mr Chen indicated that ''it is not obsolete to use planning and [state] fiats as the basis'' of administration. He also warned the party that the neglect of ''spiritual civilisation'' could lead to ''corrosion by capitalism''. Mr Chen and hardline veterans including vice-president Mr Wang Zhen have also tried to raise the political status of Premier Mr Li Peng. In recent weeks, Deng aides including vice-premier Mr Zhu Ronji have defended his high-speed growth model as well as the ''core'' status of his anointed successor, party chief Mr Jiang Zemin.